LETTER 683. TO F. MULLER. Down, January 1st, 1874.

No doubt I owe to your kindness two pamphlets received a few days ago,

which have interested me in an extraordinary degree. (683/1. This refers

to F. Muller's "Bestaubungsversuche an Abutilon-Arten" in the "Jenaische

Zeitschr." Volume VII., which are thus referred to by Darwin ("Cross

and Self Fert." pages 305-6): "Fritz Muller has shown by his valuable

experiments on hybrid Abutilons, that the union of brothers and sisters,

parents and children, and of other near relations is highly injurious to

the fertility of the offspring." The Termite paper is in the same volume

(viz., VII.) of the "Jenaische Zeitschr.") It is quite new to me what

you show about the effects of relationship in hybrids--that is to say,

as far as direct proof is concerned. I felt hardly any doubt on the

subject, from the fact of hybrids becoming more fertile when grown in

number in nursery gardens, exactly the reverse of what occurred with

Gartner. (683/2. When many hybrids are grown together the pollination by

near relatives is minimised.) The paper on Termites is even still more

interesting, and the analogy with cleistogene flowers is wonderful.

(683/3. On the back of his copy of Muller's paper Darwin wrote: "There

exist imperfectly developed male and female Termites, with wings much

shorter than those of queen and king, which serve to continue the

species if a fully developed king and queen do not after swarming (which

no doubt is for an occasional cross) enter [the] nest. Curiously like

cleistogamic flowers.") The manner in which you refer to to my chapter

on crossing is one of the most elegant compliments which I have ever

received.

I have directed to be sent to you Belt's "Nicaragua," which seems to me

the best Natural History book of travels ever published. Pray look to

what he says about the leaf-carrying ant storing the leaves up in a

minced state to generate mycelium, on which he supposes that the larvae

feed. Now, could you open the stomachs of these ants and examine the

contents, so as to prove or disprove this remarkable hypothesis? (683/4.

The hypothesis has been completely confirmed by the researches of

Moller, a nephew of F. Muller's: see his "Brasilische Pilzblumen"

("Botan. Mittheilgn. aus den Tropen," hrsg. von A.F.W. Schimper, Heft

7).)

LETTER 684. TO F. MULLER. Down, May 9th, 1877.

I have been particularly glad to receive your letter of March 25th on

Pontederia, for I am now printing a small book on heterostyled plants,

and on some allied subjects. I feel sure you will not object to my

giving a short account of the flowers of the new species which you have

sent me. I am the more anxious to do so as a writer in the United States

has described a species, and seems to doubt whether it is heterostyled,

for he thinks the difference in the length of the pistil depends merely

on its growth! In my new book I shall use all the information and

specimens which you have sent me with respect to the heterostyled

plants, and your published notices.

One chapter will be devoted to cleistogamic species, and I will just

notice your new grass case. My son Francis desires me to thank you much

for your kindness with respect to the plants which bury their seeds.

I never fail to feel astonished, when I receive one of your letters, at

the number of new facts you are continually observing. With respect to

the great supposed subterranean animal, may not the belief have arisen

from the natives having seen large skeletons embedded in cliffs? I

remember finding on the banks of the Parana a skeleton of a Mastodon,

and the Gauchos concluded that it was a borrowing animal like the

Bizcacha. (684/1. On the supposed existence in Patagonia of a gigantic

land-sloth, see "Natural Science," XIII., 1898, page 288, where

Ameghino's discovery of the skin of Neomylodon listai was practically

first made known, since his privately published pamphlet was

not generally seen. The animal was afterwards identified with a

Glossotherium, closely allied to Owen's G. Darwini, which has been named

Glossotherium listai or Grypotherium domesticum. For a good account of

the discoveries see Smith Woodward in "Natural Science," XV., 1899, page

351, where the literature is given.)

LETTER 685. TO F. MULLER. Down, May 14th [1877].

I wrote to you a few days ago to thank you about Pontederia, and now

I am going to ask you to add one more to the many kindnesses which you

have done for me. I have made many observations on the waxy secretion on

leaves which throw off water (e.g., cabbage, Tropoeolum), and I am now

going to continue my observations. Does any sensitive species of Mimosa

grow in your neighbourhood? If so, will you observe whether the leaflets

keep shut during long-continued warm rain. I find that the leaflets open

if they are continuously syringed with water at a temperature of about

19 deg C., but if the water is at a temperature of 33-35 deg C., they

keep shut for more than two hours, and probably longer. If the plant is

continuously shaken so as to imitate wind the leaflets soon open. How is

this with the native plants during a windy day? I find that some other

plants--for instance, Desmodium and Cassia--when syringed with water,

place their leaves so that the drops fall quickly off; the position

assumed differing somewhat from that in the so-called sleep. Would you

be so kind as to observe whether any [other] plants place their leaves

during rain so as to shoot off the water; and if there are any such

I should be very glad of a leaf or two to ascertain whether they are

coated with a waxy secretion. (685/1. See Letters 737-41.)

There is another and very different subject, about which I intend to

write, and should be very glad of a little information. Are earthworms

(Lumbricus) common in S. Brazil (685/2. F. Muller's reply is given in

"Vegetable Mould," page 122.), and do they throw up on the surface of

the ground numerous castings or vermicular masses such as we so commonly

see in Europe? Are such castings found in the forests beneath the dead

withered leaves? I am sure I can trust to your kindness to forgive me

for asking you so many questions.

LETTER 686. TO F. MULLER. Down, July 24th, 1878.

Many thanks for the five kinds of seeds; all have germinated, and the

Cassia seedlings have interested me much, and I daresay that I shall

find something curious in the other plants. Nor have I alone profited,

for Sir J. Hooker, who was here on Sunday, was very glad of some of the

seeds for Kew. I am particularly obliged for the information about the

earthworms. I suppose the soil in your forests is very loose, for in

ground which has lately been dug in England the worms do not come to the

surface, but deposit their castings in the midst of the loose soil.

I have some grand plants (and I formerly sent seeds to Kew) of the

cleistogamic grass, but they show no signs of producing flowers of any

kind as yet. Your case of the panicle with open flowers being sterile

is parallel to that of Leersia oryzoides. I have always fancied that

cross-fertilisation would perhaps make such panicles fertile. (686/1.

The meaning of this sentence is somewhat obscure. Darwin apparently

implies that the perfect flowers, borne on the panicles which

occasionally emerge from the sheath, might be fertile if pollinated from

another individual. See "Forms of Flowers," page 334.)

I am working away as hard as I can at all the multifarious kinds of

movements of plants, and am trying to reduce them to some simple rules,

but whether I shall succeed I do not know.

I have sent the curious lepidopteron case to Mr. Meldola.

LETTER 687. F. MULLER TO CHARLES DARWIN.

(687/1. In November, 1880, on receipt of an account of a flood in Brazil

from which Fritz Muller had barely escaped with his life ("Life and

Letters," III., 242); Darwin immediately wrote to Hermann Muller begging

to be allowed to help in making good any loss in books or scientific

instruments that his brother had sustained. It is this offer of help

that is referred to in the first paragraph of the following letter:

Darwin repeats the offer in Letter 690.)

Blumenau, Sa Catharina, Brazil, January 9th, 1881.

I do not know how to express [to] you my deep heartfelt gratitude for

the generous offer which you made to my brother on hearing of the

late dreadful flood of the Itajahy. From you, dear sir, I should have

accepted assistance without hesitation if I had been in need of it; but

fortunately, though we had to leave our house for more than a week, and

on returning found it badly damaged, my losses have not been very great.

I must thank you also for your wonderful book on the movements of

plants, which arrived here on New Year's Day. I think nobody else will

have been delighted more than I was with the results which you have

arrived at by so many admirably conducted experiments and observations;

since I observed the spontaneous revolving movement of Alisma I had seen

similar movements in so many and so different plants that I felt much

inclined to consider spontaneous revolving movement or circumnutation as

common to all plants and the movements of climbing plants as a

special modification of that general phenomenon. And this you have now

convincingly, nay, superabundantly, proved to be the case.

I was much struck with the fact that with you Maranta did not sleep for

two nights after having its leaves violently shaken by wind, for here we

have very cold nights only after storms from the west or south-west,

and it would be very strange if the leaves of our numerous species of

Marantaceae should be prevented by these storms to assume their usual

nocturnal position, just when nocturnal radiation was most to be feared.

It is rather strange, also, that Phaseolus vulgaris should not sleep

during the early part of the summer, when the leaves are most likely to

be injured during cold nights. On the contrary, it would not do any harm

to many sub-tropical plants, that their leaves must be well illuminated

during the day in order that they may assume at night a vertical

position; for, in our climate at least, cold nights are always preceded

by sunny days.

Of nearly allied plants sleeping very differently I can give you

some more instances. In the genus Olyra (at least, in the one species

observed by me) the leaves bend down vertically at night; now,

in Endlicher's "Genera plantarum" this genus immediately precedes

Strephium, the leaves of which you saw rising vertically.

In one of two species of Phyllanthus, growing as weeds near my house,

the leaves of the erect branches bend upwards at night, while in the

second species, with horizontal branches, they sleep like those of

Phyllanthus Niruri or of Cassia. In this second species the tips of

the branches also are curled downwards at night, by which movement

the youngest leaves are yet better protected. From their vertical

nyctitropic position the leaves of this Phyllanthus might return to

horizontality, traversing 90 deg, in two ways, either to their own or to

the opposite side of the branch; on the latter way no rotation would be

required, while on the former each leaf must rotate on its own axis in

order that its upper surface may be turned upwards. Thus the way to the

wrong side appears to be even less troublesome. And indeed, in some rare

cases I have seen three, four or even almost all the leaves of one side

of a branch horizontally expanded on the opposite side, with their upper

surfaces closely appressed to the lower surfaces of the leaves of that

side.

This Phyllanthus agrees with Cassia not only in its manner of sleeping,

but also by its leaves being paraheliotropic. (687/2. Paraheliotropism

is the movement by which some leaves temporarily direct their edges to

the source of light. See "Movements of Plants," page 445.) Like those of

some Cassiae its leaves take an almost perfectly vertical position, when

at noon, on a summer day, the sun is nearly in the zenith; but I doubt

whether this paraheliotropism will be observable in England. To-day,

though continuing to be fully exposed to the sun, at 3 p.m. the leaves

had already returned to a nearly horizontal position. As soon as there

are ripe seeds I will send you some; of our other species of Phyllanthus

I enclose a few seeds in this letter.

In several species of Hedychium the lateral halves of the leaves when

exposed to bright sunshine, bend downwards so that the lateral margins

meet. It is curious that a hybrid Hedychium in my garden shows scarcely

any trace of this paraheliotropism, while both the parent species are

very paraheliotropic.

Might not the inequality of the cotyledons of Citrus and of Pachira be

attributed to the pressure, which the several embryos enclosed in the

same seed exert upon each other? I do not know Pachira aquatica, but

[in] a species, of which I have a tree in my garden, all the seeds

are polyembryonic, and so were almost all the seeds of Citrus which I

examined. With Coffea arabica also seeds including two embryos are

not very rare; but I have not yet observed whether in this case the

cotyledons be inequal.

I repeated to-day Duval-Jouve's measurements on Bryophyllum calycinum

(687/3. "Power of Movement in Plants," page 237. F. Muller's

measurements show, however, that there is a tendency in the leaves to be

more highly inclined at night than in the middle of the day, and so far

they agree with Duval-Jouve's results.); but mine did not agree with

his; they are as follows:--

Distances in mm. between the tips of the upper pair of leaves.

January 9th, 1881 3 A.M. 1 P.M. 6 P.M.

1st plant 54 43 36

2nd plant 28 25 23

3rd plant 28 27 27

4th plant 51 46 39

5th plant 61 52 45

_______________________________________________

222 193 170

LETTER 688. TO F. MULLER. Down, February 23rd, 1881.

Your letter has interested me greatly, as have so many during many past

years. I thought that you would not object to my publishing in "Nature"

(688/1. "Nature," March 3rd, 1881, page 409.) some of the more striking

facts about the movements of plants, with a few remarks added to show

the bearing of the facts. The case of the Phyllanthus (688/2. See

Letter 687.), which turns up its leaves on the wrong side, is most

extraordinary and ought to be further investigated. Do the leaflets

sleep on the following night in the usual manner? Do the same leaflets

on successive nights move in the same strange manner? I was particularly

glad to hear of the strongly marked cases of paraheliotropism. I shall

look out with much interest for the publication about the figs. (688/3.

F. Muller published on Caprification in "Kosmos," 1882.) The creatures

which you sketch are marvellous, and I should not have guessed that they

were hymenoptera. Thirty or forty years ago I read all that I could find

about caprification, and was utterly puzzled. I suggested to Dr.

Cruger in Trinidad to investigate the wild figs, in relation to their

cross-fertilisation, and just before he died he wrote that he had

arrived at some very curious results, but he never published, as I

believe, on the subject.

I am extremely glad that the inundation did not so greatly injure your

scientific property, though it would have been a real pleasure to me to

have been allowed to have replaced your scientific apparatus. (688/4.

See Letter 687.) I do not believe that there is any one in the world who

admires your zeal in science and wonderful powers of observation more

than I do. I venture to say this, as I feel myself a very old man, who

probably will not last much longer.

P.S.--With respect to Phyllanthus, I think that it would be a good

experiment to cut off most of the leaflets on one side of the petiole,

as soon as they are asleep and vertically dependent; when the pressure

is thus removed, the opposite leaflets will perhaps bend beyond their

vertically dependent position; if not, the main petiole might be a

little twisted so that the upper surfaces of the dependent and now

unprotected leaflets should face obliquely the sky when the morning

comes. In this case diaheliotropism would perhaps conquer the ordinary

movements of the leaves when they awake, and [assume] their diurnal

horizontal position. As the leaflets are alternate, and as the upper

surface will be somewhat exposed to the dawning light, it is perhaps

diaheliotropism which explains your extraordinary case.

LETTER 689. TO F. MULLER. Down, April 12th, 1881.

I have delayed answering your last letter of February 25th, as I was

just sending to the printers the MS. of a very little book on the habits

of earthworms, of which I will of course send you a copy when published.

I have been very much interested by your new facts on paraheliotropism,

as I think that they justify my giving a name to this kind of movement,

about which I long doubted. I have this morning drawn up an account of

your observations, which I will send in a few days to "Nature." (689/1.

"Nature," 1881, page 603. Curious facts are given on the movements

of Cassia, Phyllanthus, sp., Desmodium sp. Cassia takes up a sunlight

position unlike its own characteristic night-position, but resembling

rather that of Haematoxylon (see "Power of Movement," figure 153, page

369). One species of Phyllanthus takes up in sunshine the nyctitropic

attitude of another species. And the same sort of relation occurs in the

genus Bauhinia.) I have thought that you would not object to my giving

precedence to paraheliotropism, which has been so little noticed. I will

send you a copy of "Nature" when published. I am glad that I was not

in too great a hurry in publishing about Lagerstroemia. (689/2.

Lagerstraemia was doubtfully placed among the heterostyled plants

("Forms of Flowers," page 167). F. Muller's observations showed that a

totally different interpretation of the two sizes of stamen is possible.

Namely, that one set serves merely to attract pollen-collecting bees,

who in the act of visiting the flowers transfer the pollen of the longer

stamens to other flowers. A case of this sort in Heeria, a Melastomad,

was described by Muller ("Nature," August 4th, 1881, page 308), and the

view was applied to the cases of Lagerstroemia and Heteranthera at

a later date ("Nature," 1883, page 364). See Letters 620-30.) I have

procured some plants of Melastomaceae, but I fear that they will not

flower for two years, and I may be in my grave before I can repeat my

trials. As far as I can imperfectly judge from my observations, the

difference in colour of the anthers in this family depends on one set

of anthers being partially aborted. I wrote to Kew to get plants with

differently coloured anthers, but I learnt very little, as describers of

dried plants do not attend to such points. I have, however, sowed seeds

of two kinds, suggested to me as probable. I have, therefore, been

extremely glad to receive the seeds of Heteranthera reniformis. As far

as I can make out it is an aquatic plant; and whether I shall succeed

in getting it to flower is doubtful. Will you be so kind as to send me

a postcard telling me in what kind of station it grows. In the course

of next autumn or winter, I think that I shall put together my notes (if

they seem worth publishing) on the use or meaning of "bloom" (689/3.

See Letters 736-40.), or the waxy secretion which makes some leaves

glaucous. I think that I told you that my experiments had led me to

suspect that the movement of the leaves of Mimosa, Desmodium and Cassia,

when shaken and syringed, was to shoot off the drops of water. If you

are caught in heavy rain, I should be very much obliged if you would

keep this notion in your mind, and look to the position of such leaves.

You have such wonderful powers of observation that your opinion would be

more valued by me than that of any other man. I have among my notes one

letter from you on the subject, but I forget its purport. I hope, also,

that you may be led to follow up your very ingenious and novel view

on the two-coloured anthers or pollen, and observe which kind is most

gathered by bees.

LETTER 690. TO F. MULLER. [Patterdale], June 21st, 1881.

I should be much obliged if you could without much trouble send me seeds

of any heterostyled herbaceous plants (i.e. a species which would

flower soon), as it would be easy work for me to raise some illegitimate

seedlings to test their degree of infertility. The plant ought not

to have very small flowers. I hope that you received the copies of

"Nature," with extracts from your interesting letters (690/1. "Nature,"

March 3rd, 1881, Volume XXIII., page 409, contains a letter from C.

Darwin on "Movements of Plants," with extracts from Fritz Muller's

letter. Another letter, "On the Movements of Leaves," was published in

"Nature," April 28th, 1881, page 603, with notes on leaf-movements sent

to Darwin by Muller.), and I was glad to see a notice in "Kosmos" on

Phyllanthus. (690/2. "Verirrte Blatter," by Fritz Muller ("Kosmos,"

Volume V., page 141, 1881). In this article an account is given of a

species of Phyllanthus, a weed in Muller's garden. See Letter 687.) I

am writing this note away from my home, but before I left I had the

satisfaction of seeing Phyllanthus sleeping. Some of the seeds which

you so kindly sent me would not germinate, or had not then germinated.

I received a letter yesterday from Dr. Breitenbach, and he tells me

that you lost many of your books in the desolating flood from which you

suffered. Forgive me, but why should you not order, through your brother

Hermann, books, etc., to the amount of 100 pounds, and I would send

a cheque to him as soon as I heard the exact amount? This would be no

inconvenience to me; on the contrary, it would be an honour and lasting

pleasure to me to have aided you in your invaluable scientific work to

this small and trifling extent. (690/3. See Letter 687, also "Life and

Letters," III., page 242.)

LETTER 691. TO F. MULLER.

(691/1. The following extract from a letter to F. Muller shows what was

the nature of Darwin's interest in the effect of carbonate of ammonia on

roots, etc. He was, we think, wrong in adhering to the belief that the

movements of aggregated masses are of an amoeboid nature. The masses

change shape, just as clouds do under the moulding action of the wind.

In the plant cell the moulding agent is the flowing protoplasm, but the

masses themselves are passive.)

September 10th, 1881.

Perhaps you may remember that I described in "Insectivorous Plants"

a really curious phenomenon, which I called the aggregation of the

protoplasm in the cells of the tentacles. None of the great German

botanists will admit that the moving masses are composed of protoplasm,

though it is astonishing to me that any one could watch the movement

and doubt its nature. But these doubts have led me to observe analogous

facts, and I hope to succeed in proving my case.

LETTER 692. TO F. MULLER. Down, November 13th, 1881.

I received a few days ago a small box (registered) containing dried

flower-heads with brown seeds somewhat sculptured on the sides. There

was no name, and I should be much obliged if some time you would tell me

what these seeds are. I have planted them.

I sent you some time ago my little book on earthworms, which, though

of no importance, has been largely read in England. I have little or

nothing to tell you about myself. I have for a couple of months been

observing the effects of carbonate of ammonia on chlorophyll and on the

roots of certain plants (692/1. Published under the title "The Action of

Carbonate of Ammonia on the Roots of Certain Plants and on Chlorophyll

Bodies," "Linn. Soc. Journ." XIX., 1882, pages 239-61, 262-84.), but the

subject is too difficult for me, and I cannot understand the meaning of

some strange facts which I have observed. The mere recording new facts

is but dull work.

Professor Wiesner has published a book (692/2. See Letter 763.), giving

a different explanation to almost every fact which I have given in my

"Power of Movement in Plants." I am glad to say that he admits that

almost all my statements are true. I am convinced that many of his

interpretations of the facts are wrong, and I am glad to hear that

Professor Pfeffer is of the same opinion; but I believe that he is

right and I wrong on some points. I have not the courage to retry all my

experiments, but I hope to get my son Francis to try some fresh ones to

test Wiesner's explanations. But I do not know why I have troubled you

with all this.

LETTER 693. TO F. MULLER. [4, Bryanston Street], December 19th, 1881.

I hope that you may find time to go on with your experiments on such

plants as Lagerstroemia, mentioned in your letter of October 29th, for

I believe you will arrive at new and curious results, more especially if

you can raise two sets of seedlings from the two kinds of pollen.

Many thanks for the facts about the effect of rain and mud in relation

to the waxy secretion. I have observed many instances of the lower side

being protected better than the upper side, in the case, as I believe,

of bushes and trees, so that the advantage in low-growing plants is

probably only an incidental one. (693/1. The meaning is here obscure: it

appears to us that the significance of bloom on the lower surface of the

leaves of both trees and herbs depends on the frequency with which all

or a majority of the stomata are on the lower surface--where they are

better protected from wet (even without the help of bloom) than on the

exposed upper surface. On the correlation between bloom and stomata, see

Francis Darwin "Linn. Soc. Journ." XXII., page 99.) As I am writing away

from my home, I have been unwilling to try more than one leaf of the

Passiflora, and this came out of the water quite dry on the lower

surface and quite wet on the upper. I have not yet begun to put my notes

together on this subject, and do not at all know whether I shall be able

to make much of it. The oddest little fact which I have observed is that

with Trifolium resupinatum, one half of the leaf (I think the right-hand

side, when the leaf is viewed from the apex) is protected by waxy

secretion, and not the other half (693/2. In the above passage "leaf"

should be "leaflet": for a figure of Trifolium resupinatum see Letter

740.); so that when the leaf is dipped into water, exactly half the leaf

comes out dry and half wet. What the meaning of this can be I cannot

even conjecture. I read last night your very interesting article in

"Kosmos" on Crotalaria, and so was very glad to see the dried leaves

sent by you: it seems to me a very curious case. I rather doubt whether

it will apply to Lupinus, for, unless my memory deceives me, all the

leaves of the same plant sometimes behaved in the same manner; but I

will try and get some of the same seeds of the Lupinus, and sow them in

the spring. Old age, however, is telling on me, and it troubles me to

have more than one subject at a time on hand.

(693/3. In a letter to F. Muller (September 10, 1881) occurs a sentence

which may appropriately close this series: "I often feel rather ashamed

of myself for asking for so many things from you, and for taking up so

much of your valuable time, but I can assure you that I feel grateful.")

2.XI.III. MISCELLANEOUS, 1868-1881.

LETTER 694. TO G. BENTHAM. Down, April 22nd, 1868.

I have been extremely much pleased by your letter, and I take it as

a very great compliment that you should have written to me at such

length...I am not at all surprised that you cannot digest pangenesis:

it is enough to give any one an indigestion; but to my mind the idea

has been an immense relief, as I could not endure to keep so many large

classes of facts all floating loose in my mind without some thread of

connection to tie them together in a tangible method.

With respect to the men who have recently written on the crossing

of plants, I can at present remember only Hildebrand, Fritz Muller,

Delpino, and G. Henslow; but I think there are others. I feel sure that

Hildebrand is a very good observer, for I have read all his papers, and

during the last twenty years I have made unpublished observations on

many of the plants which he describes. [Most of the criticisms which I

sometimes meet with in French works against the frequency of crossing I

am certain are the result of mere ignorance. I have never hitherto found

the rule to fail that when an author describes the structure of a flower

as specially adapted for self-fertilisation, it is really adapted for

crossing. The Fumariaceae offer a good instance of this, and Treviranus

threw this order in my teeth; but in Corydalis Hildebrand shows how

utterly false the idea of self-fertilisation is. This author's paper

on Salvia (694/1. Hildebrand, "Pringsheim's Jahrbucher," IV.) is really

worth reading, and I have observed some species, and know that he is

accurate]. (694/2. The passage within [] was published in the "Life

and Letters," III., page 279.) Judging from a long review in the "Bot.

Zeitung", and from what I know of some the plants, I believe Delpino's

article especially on the Apocynaea, is excellent; but I cannot read

Italian. (694/3. Hildebrand's paper in the "Bot. Zeitung," 1867, refers

to Delpino's work on the Asclepiads, Apocyneae and other Orders.)

Perhaps you would like just to glance at such pamphlets as I can lay my

hands on, and therefore I will send them, as if you do not care to see

them you can return them at once; and this will cause you less trouble

than writing to say you do not care to see them. With respect to

Primula, and one point about which I feel positive is that the Bardfield

and common oxlips are fundamentally distinct plants, and that the

common oxlip is a sterile hybrid. (694/4. For a general account of

the Bardfield oxlip (Primula elatior) see Miller Christy, "Linn. Soc.

Journ." Volume XXXIII., page 172, 1897.) I have never heard of the

common oxlip being found in great abundance anywhere, and some amount

of difference in number might depend on so small a circumstance as the

presence of some moth which habitually sucked the primrose and cowslip.

To return to the subject of crossing: I am experimenting on a very large

scale on the difference in power and growth between plants raised from

self-fertilised and crossed seeds, and it is no exaggeration to say that

the difference in growth and vigour is sometimes truly wonderful. Lyell,

Huxley, and Hooker have seen some of my plants, and been astonished; and

I should much like to show them to you. I always supposed until lately

that no evil effects would be visible until after several generations

of self-fertilisation, but now I see that one generation sometimes

suffices, and the existence of dimorphic plants and all the wonderful

contrivances of orchids are quite intelligible to me.

LETTER 695. TO T.H. FARRER (Lord Farrer). Down, June 5th, 1868.

I must write a line to cry peccavi. I have seen the action in Ophrys

exactly as you describe, and am thoroughly ashamed of my inaccuracy.

(695/1. See "Fertilisation of Orchids," Edition II., page 46, where

Lord Farrer's observations on the movement of the pollinia in Ophrys

muscifera are given.) I find that the pollinia do not move if kept in a

very damp atmosphere under a glass; so that it is just possible, though

very improbable, that I may have observed them during a very damp day.

I am not much surprised that I overlooked the movement in Habenaria, as

it takes so long. (695/2. This refers to Peristylus viridis, sometimes

known as Habenaria viridis. Lord Farrer's observations are given in

"Fertilisation of Orchids," Edition II., page 63.)

I am glad you have seen Listera; it requires to be seen to believe in

the co-ordination in the position of the parts, the irritability,

and the chemical nature of the viscid fluid. This reminds me that

I carefully described to Huxley the shooting out of the pollinia in

Catasetum, and received for an answer, "Do you really think that I can

believe all that!" (695/3. See Letter 665.)

LETTER 696. TO J.D. HOOKER. Down, December 2nd, 1868.

It is a splendid scheme, and if you make only a beginning on a "Flora,"

which shall serve as an index to all papers on curious points in the

life-history of plants, you will do an inestimable good service. Quite

recently I was asked by a man how he could find out what was known on

various biological points in our plants, and I answered that I knew of

no such book, and that he might ask half a dozen botanists before one

would chance to remember what had been published on this or that point.

Not long ago another man, who had been experimenting on the quasi-bulbs

on the leaves of Cardamine, wrote to me to complain that he could not

find out what was known on the subject. It is almost certain that some

early or even advanced students, if they found in their "Flora" a

line or two on various curious points, with references for further

investigation, would be led to make further observations. For instance,

a reference to the viscid threads emitted by the seeds of Compositae, to

the apparatus (if it has been described) by which Oxalis spurts out its

seeds, to the sensitiveness of the young leaves of Oxalis acetosella

with reference to O. sensitiva. Under Lathyrus nissolia it would [be]

better to refer to my hypothetical explanation of the grass-like leaves

than to nothing. (696/1. No doubt the view given in "Climbing Plants,"

page 201, that L. nissolia has been evolved from a form like L. aphaca.)

Under a twining plant you might say that the upper part of the shoot

steadily revolves with or against the sun, and so, when it strikes

against any object it turns to the right or left, as the case may be.

If, again, references were given to the parasitism of Euphrasia,

etc., how likely it would be that some young man would go on with the

investigation; and so with endless other facts. I am quite enthusiastic

about your idea; it is a grand idea to make a "Flora" a guide for

knowledge already acquired and to be acquired. I have amused myself by

speculating what an enormous number of subjects ought to be introduced

into a Eutopian (696/2. A mis-spelling of Utopian.) Flora, on the

quickness of the germination of the seeds, on their means of dispersal;

on the fertilisation of the flower, and on a score of other points,

about almost all of which we are profoundly ignorant. I am glad to read

what you say about Bentham, for my inner consciousness tells me that

he has run too many forms together. Should you care to see an elaborate

German pamphlet by Hermann Muller on the gradation and distinction of

the forms of Epipactis and of Platanthera? (696/3. "Verhand. d. Nat.

Ver. f. Pr. Rh. u. Wesfal." Jahrg. XXV.: see "Fertilisation of Orchids,"

Edition II., pages 74, 102.) It may be absurd in me to suggest, but I

think you would find curious facts and references in Lecoq's enormous

book (696/4. "Geographie Botanique," 9 volumes, 1854-58.), in Vaucher's

four volumes (696/5. "Plantes d'Europe," 4 volumes, 1841.), in

Hildebrand's "Geschlechter Vertheilung" (696/6 "Geschlechter Vertheilung

bei den Pflanzen," 1 volume, Leipzig, 1867.), and perhaps in Fournier's

"De la Fecondation." (696/7. "De la Fecondation dans les Phanerogames,"

par Eugene Fournier: thesis published in Paris in 1863. The facts noted

in Darwin's copy are the explosive stamens of Parietaria, the submerged

flowers of Alisma containing air, the manner of fertilisation of

Lopezia, etc.) I wish you all success in your gigantic undertaking;

but what a pity you did not think of it ten years ago, so as to have

accumulated references on all sorts of subjects. Depend upon it, you

will have started a new era in the floras of various countries. I can

well believe that Mrs. Hooker will be of the greatest possible use to

you in lightening your labours and arranging your materials.

LETTER 697. TO J.D. HOOKER. Down, December 5th, 1868.

...Now I want to beg for assistance for the new edition of "Origin."

Nageli himself urges that plants offer many morphological differences,

which from being of no service cannot have been selected, and which he

accounts for by an innate principle of progressive development. (697/1.

Nageli's "Enstehung und Begriff der Naturhistorischen Art." An address

delivered at the public session of the Royal Academy of Sciences of

Munich, March 28th, 1865; published by the Academy. Darwin's copy is the

2nd edition; it bears signs, in the pencilled notes on the margins, of

having been read with interest. Much of it was translated for him by a

German lady, whose version lies with the original among his pamphlets.

At page 27 Nageli writes: "It is remarkable that the useful adaptations

which Darwin brings forward in the case of animals, and which may be

discovered in numbers among plants, are exclusively of a physiological

kind, that they always show the formation or transformation of an

organ to a special function. I do not know among plants a morphological

modification which can be explained on utilitarian principles." Opposite

this passage Darwin has written "a very good objection": but Nageli's

sentence seems to us to be of the nature of a truism, for it is clear

that any structure whose evolution can be believed to have come about

by Natural Selection must have a function, and the case falls into

the physiological category. The various meanings given to the term

morphological makes another difficulty. Nageli cannot use it in the

sense of "structural"--in which sense it is often applied, since that

would mean that no plant structures have a utilitarian origin. The

essence of morphology (in the better and more precise sense) is descent;

thus we say that a pollen-grain is morphologically a microspore. And

this very example serves to show the falseness of Nageli's view, since

a pollen-grain is an adaptation to aerial as opposed to aquatic

fertilisation. In the 5th edition of the "Origin," 1869, page 151,

Darwin discusses Nageli's essay, confining himself to the simpler

statement that there are many structural characters in plants to which

we cannot assign uses. See Volume I., Letter 207.) I find old notes

about this difficulty; but I have hitherto slurred it over. Nageli gives

as instances the alternate and spiral arrangement of leaves, and the

arrangement of the cells in the tissues. Would you not consider as a

morphological difference the trimerous, tetramerous, etc., divisions

of flowers, the ovules being erect or suspended, their attachment being

parietal or placental, and even the shape of the seed when of no service

to the plant.

Now, I have thought, and want to show, that such differences follow in

some unexplained manner from the growth or development of plants which

have passed through a long series of adaptive changes. Anyhow, I want

to show that these differences do not support the idea of progressive

development. Cassini states that the ovaria on the circumference and

centre of Compos. flowers differ in essential characters, and so do

the seeds in sculpture. The seeds of Umbelliferae in the same relative

positions are coelospermous and orthospermous. There is a case given by

Augt. St. Hilaire of an erect and suspended ovule in the same ovarium,

but perhaps this hardly bears on the point. The summit flower, in Adoxa

and rue differ from the lower flowers. What is the difference in flowers

of the rue? how is the ovarium, especially in the rue? As Augt. St.

Hilaire insists on the locularity of the ovarium varying on the same

plant in some of the Rutaceae, such differences do not speak, as it

seems to me, in favour of progressive development. Will you turn

the subject in your mind, and tell me any more facts. Difference in

structure in flowers in different parts of the same plant seems best

to show that they are the result of growth or position or amount of

nutriment.

I have got your photograph (697/2. A photograph by Mrs. Cameron.) over

my chimneypiece, and like it much; but you look down so sharp on me that

I shall never be bold enough to wriggle myself out of any contradiction.

Owen pitches into me and Lyell in grand style in the last chapter of

volume 3 of "Anat. of Vertebrates." He is a cool hand. He puts words

from me in inverted commas and alters them. (697/3. The passage referred

to seems to be in Owen's "Anatomy of Vertebrata," III., pages 798, 799,

note. "I deeply regretted, therefore, to see in a 'Historical Sketch'

of the Progress of Enquiry into the origin of species, prefixed to the

fourth edition of that work (1866), that Mr. Darwin, after affirming

inaccurately and without evidence, that I admitted Natural Selection to

have done something toward that end, to wit, the 'origin of species,'

proceeds to remark: 'It is surprising that this admission should not

have been made earlier, as Prof. Owen now believes that he promulgated

the theory of Natural Selection in a passage read before the Zoological

Society in February, 1850, ("Trans." Volume IV., page 15).'" The first

of the two passages quoted by Owen from the fourth edition of the

"Origin" runs: "Yet he [Prof. Owen] at the same time admits that Natural

Selection MAY [our italics] have done something towards this end." In

the sixth edition of the "Origin," page xviii., Darwin, after referring

to a correspondence in the "London Review" between the Editor of that

Journal and Owen, goes on: "It appeared manifest to the editor, as well

as to myself, that Prof. Owen claimed to have promulgated the theory of

Natural Selection before I had done so;...but as far as it is possible

to understand certain recently published passages (Ibid. ["Anat. of

Vert."], Volume III., page 798), I have either partly or wholly again

fallen into error. It is consolatory to me that others find Prof. Owen's

controversial writings as difficult to understand and to reconcile with

each other, as I do. As far as the mere enunciation of the principle

of Natural Selection is concerned, it is quite immaterial whether or

no Prof. Owen preceded me, for both of us, as shown in this historical

sketch, were long ago preceded by Dr. Wells and Mr. Matthews.")

LETTER 698. TO J.D. HOOKER. Down, December 29th, 1868.

Your letter is quite invaluable, for Nageli's essay (698/1. See

preceding Letter.) is so clever that it will, and indeed I know it has

produced a great effect; so that I shall devote three or four pages

to an answer. I have been particularly struck by your statements about

erect and suspended ovules. You have given me heart, and I will fight my

battle better than I should otherwise have done. I think I cannot resist

throwing the contrivances in orchids into his teeth. You say nothing

about the flowers of the rue. (698/2. For Ruta see "Origin," Edition

V., page 154.) Ask your colleagues whether they know anything about the

structure of the flower and ovarium in the uppermost flower. But don't

answer on purpose.

I have gone through my long Index of "Gardeners' Chronicle," which was

made solely for my own use, and am greatly disappointed to find, as I

fear, hardly anything which will be of use to you. (698/3. For Hooker's

projected biological book, see Letter 696.) I send such as I have for

the chance of their being of use.

LETTER 699. TO J.D. HOOKER. Down, January 16th [1869].

Your two notes and remarks are of the utmost value, and I am greatly

obliged to you for your criticism on the term. "Morphological" seems

quite just, but I do not see how I can avoid using it. I found, after

writing to you, in Vaucher about the Rue (699/1. "Plantes d'Europe,"

Volume I., page 559, 1841.), but from what you say I will speak more

cautiously. It is the Spanish Chesnut that varies in divergence. Seeds

named Viola nana were sent me from Calcutta by Scott. I must refer

to the plants as an "Indian species," for though they have produced

hundreds of closed flowers, they have not borne one perfect flower.

(699/2. The cleistogamic flowers of Viola are used in the discussion on

Nageli's views. See "Origin," Edition V., page 153.) You ask whether I

want illustrations "of ovules differing in position in different flowers

on the same plant." If you know of such cases, I should certainly much

like to hear them. Again you speak of the angle of leaf-divergence

varying and the variations being transmitted. Was the latter point put

in in a hurry to round the sentence, or do you really know of cases?

Whilst looking for notes on the variability of the divisions of the

ovarium, position of the ovules, aestivation, etc., I found remarks

written fifteen or twenty years ago, showing that I then supposed that

characters which were nearly uniform throughout whole groups must be

of high vital importance to the plants themselves; consequently I was

greatly puzzled how, with organisms having very different habits

of life, this uniformity could have been acquired through Natural

Selection. Now, I am much inclined to believe, in accordance with

the view given towards the close of my MS., that the near approach

to uniformity in such structures depends on their not being of vital

importance, and therefore not being acted on by Natural Selection.

(699/3. This view is given in the "Origin," Edition VI., page 372.) If

you have reflected on this point, what do you think of it? I hope that

you approved of the argument deduced from the modifications in the small

closed flowers.

It is only about two years since last edition of "Origin," and I am

fairly disgusted to find how much I have to modify, and how much I ought

to add; but I have determined not to add much. Fleeming Jenkin has given

me much trouble, but has been of more real use to me than any other

essay or review. (699/4. On Fleeming Jenkin's review, "N. British

Review," June, 1867, see "Life and Letters," III., page 107.)

LETTER 700. TO J.D. HOOKER. Down [January 22nd, 1869].

Your letter is quite splenditious. I am greatly tempted, but shall,

I hope, refrain from using some of your remarks in my chapter on

Classification. It is very true what you say about unimportant

characters being so important systematically; yet it is hardly

paradoxical bearing in mind that the natural system is genetic, and that

we have to discover the genealogies anyhow. Hence such parts as organs

of generation are so useful for classification though not concerned with

the manner of life. Hence use for same purpose of rudimentary organs,

etc. You cannot think what a relief it is that you do not object to this

view, for it removes PARTLY a heavy burden from my shoulders. If I lived

twenty more years and was able to work, how I should have to modify the

"Origin," and how much the views on all points will have to be modified!

Well, it is a beginning, and that is something...

LETTER 701. TO T.H. FARRER (Lord Farrer). Down, August 10th, 1869.

Your view seems most ingenious and probable; but ascertain in a good

many cases that the nectar is actually within the staminal tube.

(701/1. It seems that Darwin did not know that the staminal tube in

the diadelphous Leguminosae serves as a nectar-holder, and this is

surprising, as Sprengel was aware of the fact.) One can see that if

there is to be a split in the tube, the law of symmetry would lead it

to be double, and so free one stamen. Your view, if confirmed, would be

extremely well worth publication before the Linnean Society. It is to me

delightful to see what appears a mere morphological character found

to be of use. It pleases me the more as Carl Nageli has lately been

pitching into me on this head. Hooker, with whom I discussed the

subject, maintained that uses would be found for lots more structures,

and cheered me by throwing my own orchids into my teeth. (701/2. See

Letters 697-700.)

All that you say about changed position of the peduncle in bud, in

flower, and in seed, is quite new to me, and reminds me of analogous

cases with tendrils. (701/3. See Vochting, "Bewegung der Bluthen und

Fruchte," 1882; also Kerner, "Pflanzenleben," Volume I., page 494,

Volume II., page 121.) This is well worth working out, and I dare say

the brush of the stigma.

With respect to the hairs or filaments (about which I once spoke) within

different parts of flowers, I have a splendid Tacsonia with perfectly

pendent flowers, and there is only a microscopical vestige of the corona

of coloured filaments; whilst in most common passion-flowers the flowers

stand upright, and there is the splendid corona which apparently would

catch pollen. (701/4. Sprengel ("Entdeckte Geheimniss," page 164)

imagined that the crown of the Passion-flower served as a nectar-guide

and as a platform for insects, while other rings of filaments served

to keep rain from the nectar. F. Muller, quoted in H. Muller

("Fertilisation," page 268), looks at the crowns of hairs, ridges in

some species, etc., as gratings serving to imprison flies which attract

the fertilising humming-birds. There is, we believe, no evidence that

the corona catches pollen. See Letter 704, note.)

On the lower side of corolla of foxglove there are some fine hairs, but

these seem of not the least use (701/5. It has been suggested that the

hairs serve as a ladder for humble bees; also that they serve to keep

out "unbidden guests.")--a mere purposeless exaggeration of down on

outside--as I conclude after watching the bees at work, and afterwards

covering up some plants; for the protected flowers rarely set any seed,

so that the hairy lower part of corolla does not come into contact with

stigma, as some Frenchman says occurs with some other plants, as Viola

odorata and I think Iris.

I heartily wish I could accept your kind invitation, for I am not by

nature a savage, but it is impossible. Forgive my dreadful handwriting,

none of my womenkind are about to act as amanuensis.

LETTER 702. TO WILLIAM C. TAIT.

(702/1. Mr. Tait, to whom the following letter is addressed, was

resident in Portugal. His kindness in sending plants of Drosophyllum

lusitanicum is acknowledged in "Insectivorous Plants.")

Down, March 12th, 1869.

I have received your two letters of March 2nd and 5th, and I really do

not know how to thank you enough for your extraordinary kindness and

energy. I am glad to hear that the inhabitants notice the power of the

Drosophyllum to catch flies, for this is the subject of my studies.

(702/2. The natives are said to hang up plants of Drosophyllum in their

cottages to act as fly-papers ("Insectivorous Plants," page 332).) I

have observed during several years the manner in which this is effected,

and the results produced in several species of Drosera, and in the

wonderful American Dionoea, the leaves of which catch insects just like

a steel rat-trap. Hence I was most anxious to learn how the Drosophyllum

would act, so that the Director of the Royal Gardens at Kew wrote some

years ago to Portugal to obtain specimens for me, but quite failed.

So you see what a favour you have conferred on me. With Drosera it is

nothing less than marvellous how minute a fraction of a grain of any

nitrogenised matter the plant can detect; and how differently it behaves

when matter, not containing nitrogen, of the same consistence, whether

fluid or solid, is applied to the glands. It is also exquisitely

sensitive to a weight of even the 1/70000 of a grain. From what I can

see of the glands on Drosophyllum I suspect that I shall find only

the commencement, or nascent state of the wonderful capacities of the

Drosera, and this will be eminently interesting to me. My MS. on this

subject has been nearly ready for publication during some years, but

when I shall have strength and time to publish I know not.

And now to turn to other points in your letter. I am quite ignorant of

ferns, and cannot name your specimen. The variability of ferns passes

all bounds. With respect to your Laugher Pigeons, if the same with

the two sub-breeds which I kept, I feel sure from the structure of

the skeleton, etc., that it is a descendant of C. livia. In regard

to beauty, I do not feel the difficulty which you and some others

experience. In the last edition of my "Origin" I have discussed the

question, but necessarily very briefly. (702/3. Fourth Edition, page

238.) A new and I hope amended edition of the "Origin" is now passing

through the press, and will be published in a month or two, and it will

give me great pleasure to send you a copy. Is there any place in London

where parcels are received for you, or shall I send it by post? With

reference to dogs' tails, no doubt you are aware that a rudimentary

stump is regularly inherited by certain breeds of sheep-dogs, and by

Manx cats. You speak of a change in the position of the axis of the

earth: this is a subject quite beyond me, but I believe the astronomers

reject the idea. Nevertheless, I have long suspected that some

periodical astronomical or cosmical cause must be the agent of the

incessant oscillations of level in the earth's crust. About a month

ago I suggested this to a man well capable of judging, but he could not

conceive any such agency; he promised, however, to keep it in mind. I

wish I had time and strength to write to you more fully. I had intended

to send this letter off at once, but on reflection will keep it till I

receive the plants.

LETTER 703. TO H. MULLER. Down, March 14th, 1870.

I think you have set yourself a new, very interesting, and difficult

line of research. As far as I know, no one has carefully observed the

structure of insects in relation to flowers, although so many have

now attended to the converse relation. (703/1. See Letter 462, also H.

Muller, "Fertilisation of Flowers," English Translation, page 30, on

"The insects which visit flowers." In Muller's book references are

given to several of his papers on this subject.) As I imagine few or

no insects are adapted to suck the nectar or gather the pollen of

any single family of plants, such striking adaptations can hardly, I

presume, be expected in insects as in flowers.

LETTER 704. TO T.H. FARRER (Lord Farrer).

Down, May 28th, 1870.

I suppose I must have known that the stamens recovered their former

position in Berberis (704/1. See Farrer, "Nature," II., 1870, page 164.

Lord Farrer was before H. Muller in making out the mechanism of the

barberry.), for I formerly tried experiments with anaesthetics, but I

had forgotten the facts, and I quite agree with you that it is a

sound argument that the movement is not for self-fertilisation. The

N. American barberries (Mahonia) offer a good proof to what an extent

natural crossing goes on in this genus; for it is now almost impossible

in this country to procure a true specimen of the two or three forms

originally introduced.

I hope the seeds of Passiflora will germinate, for the turning up of the

pendent flower must be full of meaning. (704/2. Darwin had (May 12th,

1870) sent to Farrer an extract from a letter from F. Muller, containing

a description of a Passiflora visited by humming-birds, in which the

long flower-stalk curls up so that "the flower itself is upright."

Another species visited by bees is described as having "dependent

flowers." In a letter, June 29th, 1870, Mr. Farrer had suggested that P.

princeps, which he described as having sub-erect flowers, is fitted for

humming-birds' visits. In another letter, October 13th, 1869, he

says that Tacsonia, which has pendent flowers and no corona, is not

fertilised by insects in English glass-houses, and may be adapted for

humming-birds. See "Life and Letters," III., page 279, for Farrer's

remarks on Tacsonia and Passiflora; also H. Muller's "Fertilisation of

Flowers," page 268, for what little is known on the subject; also Letter

701 in the present volume.) I am so glad that you are able to occupy

yourself a little with flowers: I am sure it is most wise in you, for

your own sake and children's sakes.

Some little time ago Delpino wrote to me praising the Swedish book on

the fertilisation of plants; as my son George can read a little Swedish,

I should like to have it back for a time, just to hear a little what it

is about, if you would be so kind as to return it by book-post.

(704/3. Severin Axell, "Om anordningarna for de Fanerogama Vaxternas

Befruktning," Stockholm, 1869.)

I am going steadily on with my experiments on the comparative growth

of crossed and self-fertilised plants, and am now coming to some very

curious anomalies and some interesting results. I forget whether I

showed you any of them when you were here for a few hours. You ought

to see them, as they explain at a glance why Nature has taken such

extraordinary pains to ensure frequent crosses between distinct

individuals.

If in the course of the summer you should feel any inclination to come

here for a day or two, I hope that you will propose to do so, for we

should be delighted to see you...

LETTER 705. TO ASA GRAY. Down, December 7th, 1870.

I have been very glad to receive your letter this morning. I have for

some time been wishing to write to you, but have been half worked to

death in correcting my uncouth English for my new book. (705/1.

"Descent of Man.") I have been glad to hear of your cases appearing like

incipient dimorphism. I believe that they are due to mere variability,

and have no significance. I found a good instance in Nolana prostrata,

and experimented on it, but the forms did not differ in fertility. So it

was with Amsinckia, of which you told me. I have long thought that such

variations afforded the basis for the development of dimorphism. I was

not aware of such cases in Phlox, but have often admired the arrangement

of the anthers, causing them to be all raked by an inserted proboscis. I

am glad also to hear of your curious case of variability in ovules, etc.

I said that I had been wishing to write to you, and this was about your

Drosera, which after many fluctuations between life and death, at last

made a shoot which I could observe. The case is rather interesting; but

I must first remind you that the filament of Dionoea is not sensitive

to very light prolonged pressure, or to nitrogenous matter, but is

exquisitely sensitive to the slightest touch. (705/2. In another

connection the following reference to Dionoea is of some interest: "I am

sure I never heard of Curtis's observations on Dionoea, nor have I met

with anything more than general statements about this plant or about

Nepenthes catching insects." (From a letter to Sir J.D. Hooker, July

12th, 1860.)) In our Drosera the filaments are not sensitive to a slight

touch, but are sensitive to prolonged pressure from the smallest object

of any nature; they are also sensitive to solid or fluid nitrogenous

matter. Now in your Drosera the filaments are not sensitive to a rough

touch or to any pressure from non-nitrogenous matter, but are sensitive

to solid or fluid nitrogenous matter. (705/3. Drosera filiformis: see

"Insectivorous Plants," page 281. The above account does not entirely

agree with Darwin's published statement. The filaments moved when bits

of cork or cinder were placed on them; they did not, however, respond

to repeated touches with a needle, thus behaving differently from D.

rotundifolia. It should be remembered that the last-named species is

somewhat variable in reacting to repeated touches.) Is it not curious

that there should be such diversified sensitiveness in allied plants?

I received a very obliging letter from Mr. Morgan, but did not see him,

as I think he said he was going to start at once for the Continent. I am

sorry to hear rather a poor account of Mrs. Gray, to whom my wife and I

both beg to be very kindly remembered.

LETTER 706. TO C.V. RILEY.

(706/1. In Riley's opinion his most important work was the series

entitled "Annual Report on the Noxious, Beneficial, and other Insects

of the State of Missouri" (Jefferson City), beginning in 1869. These

reports were greatly admired by Mr. Darwin, and his copies of them,

especially of Nos. 3 and 4, show signs of careful reading.)

Down, June 1st [1871].

I received some little time ago your report on noxious insects, and have

now read the whole with the greatest interest. (706/2. "Third Annual

Report on the Noxious, Beneficial, and other Insects of the State of

Missouri" (Jefferson City, Mo.). The mimetic case occurs at page 67; the

1875 pupae of Pterophorus periscelidactylus, the "Grapevine Plume," have

pupae either green or reddish brown, the former variety being found on

the leaves, the latter on the brown stems of the vine.) There are a vast

number of facts and generalisations of value to me, and I am struck with

admiration at your powers of observation.

The discussion on mimetic insects seems to me particularly good and

original. Pray accept my cordial thanks for the instruction and interest

which I have received.

What a loss to Natural Science our poor mutual friend Walsh has been; it

is a loss ever to be deplored...

Your country is far ahead of ours in some respects; our Parliament would

think any man mad who should propose to appoint a State Entomologist.

LETTER 707A. TO C.V. RILEY.

(706A/1. We have found it convenient to place the two letters to Riley

together, rather than separate them chronologically.)

Down, September 28th, 1881.

I must write half a dozen lines to say how much interested I have been

by your "Further Notes" on Pronuba which you were so kind as to send me.

(706A/2. "Proc. Amer. Assoc. Adv. Sci." 1880.) I had read the various

criticisms, and though I did not know what answer could be made, yet I

felt full confidence in your result, and now I see that I was right...If

you make any further observation on Pronuba it would, I think, be well

worth while for you to observe whether the moth can or does occasionally

bring pollen from one plant to the stigma of a distinct one (706A/3.

Riley discovered the remarkable fact that the Yucca moth (Pronuba

yuccasella) lays its eggs in the ovary of Yucca flowers, which it has

previously pollinated, thus making sure of a supply of ovules for the

larvae.), for I have shown that the cross-fertilisation of the flowers

on the same plant does very little good; and, if I am not mistaken,

you believe that Pronuba gathers pollen from the same flower which she

fertilises.

What interesting and beautiful observations you have made on the

metamorphoses of the grasshopper-destroying insects.

LETTER 707. TO F. HILDEBRAND. Down, February 9th [1872].

Owing to other occupations I was able to read only yesterday your

paper on the dispersal of the seeds of Compositae. (707/1. "Ueber die

Verbreitungsmittel der Compositenfruchte." "Bot. Zeitung," 1872, page

1.) Some of the facts which you mention are extremely interesting.

I write now to suggest as worthy of your examination the curious

adhesive filaments of mucus emitted by the achenia of many Compositae,

of which no doubt you are aware. My attention was first called to the

subject by the achenia of an Australian Pumilio (P. argyrolepis), which

I briefly described in the "Gardeners' Chronicle," 1861, page 5. As the

threads of mucus dry and contract they draw the seeds up into a vertical

position on the ground. It subsequently occurred to me that if these

seeds were to fall on the wet hairs of any quadruped they would adhere

firmly, and might be carried to any distance. I was informed that

Decaisne has written a paper on these adhesive threads. What is the

meaning of the mucus so copiously emitted from the moistened seeds of

Iberis, and of at least some species of Linum? Does the mucus serve as

a protection against their being devoured, or as a means of attachment.

(707/2. Various theories have been suggested, e.g., that the slime by

anchoring the seed to the soil facilitates the entrance of the radicle

into the soil: the slime has also been supposed to act as a temporary

water-store. See Klebs in Pfeffer's "Untersuchungen aus dem Bot. Inst.

zu Tubingen," I., page 581.) I have been prevented reading your paper

sooner by attempting to read Dr. Askenasy's pamphlet, but the German is

too difficult for me to make it all out. (707/3. E. Askenasy, "Beitrage

zur Kritik der Darwin'schen Lehre." Leipzig, 1872.) He seems to follow

Nageli completely. I cannot but think that both much underrate the

utility of various parts of plants; and that they greatly underrate

the unknown laws of correlated growth, which leads to all sorts of

modifications, when some one structure or the whole plant is modified

for some particular object.

LETTER 708. TO T.H. FARRER. (Lord Farrer).

(708/1. The following letter refers to a series of excellent

observations on the fertilisation of Leguminosae, made by Lord Farrer in

the autumn of 1869, in ignorance of Delpino's work on the subject. The

result was published in "Nature," October 10th and 17th, 1872, and

is full of interesting suggestions. The discovery of the mechanism in

Coronilla mentioned in a note was one of the cases in which Lord Farrer

was forestalled.)

Down [1872].

I declare I am almost as sorry as if I had been myself

forestalled--indeed, more so, for I am used to it. It is, however, a

paramount, though bothersome duty in every naturalist to try and make

out all that has been done by others on the subject. By all means

publish next summer your confirmation and a summary of Delpino's

observations, with any new ones of your own. Especially attend about the

nectary exterior to the staminal tube. (708/2. This refers to a species

of Coronilla in which Lord Farrer made the remarkable discovery that the

nectar is secreted on the outside of the calyx. See "Nature," July 2nd,

1874, page 169; also Letter 715.) This will in every way be far better

than writing to Delpino. It would not be at all presumptuous in you to

criticise Delpino. I am glad you think him so clever; for so it struck

me.

Look at hind legs yourself of some humble and hive-bees; in former take

a very big individual (if any can be found) for these are the females,

the males being smaller, and they have no pollen-collecting apparatus.

I do not remember where it is figured--probably in Kirby & Spence--but

actual inspection better...

Please do not return any of my books until all are finished, and do not

hurry.

I feel certain you will make fine discoveries.

LETTER 709. TO T.H. FARRER. (Lord Farrer). Sevenoaks, October 13th,

1872.

I must send you a line to say how extremely good your article appears to

me to be. It is even better than I thought, and I remember thinking it

very good. I am particularly glad of the excellent summary of evidence

about the common pea, as it will do for me hereafter to quote; nocturnal

insects will not do. I suspect that the aboriginal parent had bluish

flowers. I have seen several times bees visiting common and sweet

peas, and yet varieties, purposely grown close together, hardly ever

intercross. This is a point which for years has half driven me mad,

and I have discussed it in my "Var. of Animals and Plants under Dom."

(709/1. In the second edition (1875) of the "Variation of Animals and

Plants," Volume I., page 348, Darwin added, with respect to the rarity

of spontaneous crosses in Pisum: "I have reason to believe that this

is due to their stignas being prematurely fertilised in this country

by pollen from the same flower." This explanation is, we think, almost

certainly applicable to Lathyrus odoratus, though in Darwin's latest

publication on the subject he gives reasons to the contrary. See "Cross

and Self-Fertilisation," page 156, where the problem is left unsolved.

Compare Letter 714 to Delpino. In "Life and Letters," III., page 261,

the absence of cross-fertilisation is explained as due to want of

perfect adaptation between the pea and our native insects. This is

Hermann Muller's view: see his "Fertilisation of Flowers," page 214.

See Letter 583, note.) I now suspect (and I wish I had strength to

experimentise next spring) that from changed climate both species

are prematurely fertilised, and therefore hardly ever cross. When

artificially crossed by removal of own pollen in bud, the offspring are

very vigorous.

Farewell.--I wish I could compel you to go on working at fertilisation

instead of so insignificant a subject as the commerce of the country!

You pay me a very pretty compliment at the beginning of your paper.

LETTER 710. TO J.D. HOOKER.

(710/1. The following letters to Sir J.D. Hooker and the late Mr.

Moggridge refer to Moggridge's observation that seeds stored in the nest

of the ant Atta at Mentone do not germinate, though they are certainly

not dead. Moggridge's observations are given in his book, "Harvesting

Ants and Trap-Door Spiders," 1873, which is full of interesting details.

The book is moreover remarkable in having resuscitated our knowledge of

the existence of the seed-storing habit. Mr. Moggridge points out that

the ancients were familiar with the facts, and quotes the well-known

fable of the ant and the grasshopper, which La Fontaine borrowed from

Aesop. Mr. Moggridge (page 5) goes on: "So long as Europe was taught

Natural History by southern writers the belief prevailed; but no sooner

did the tide begin to turn, and the current of information to flood from

north to south, than the story became discredited."

In Moggridge's "supplement" on the same subject, published in 1874, the

author gives an account of his experiments made at Darwin's suggestion,

and concludes (page 174) that "the vapour of formic acid is incapable

of rendering the seeds dormant after the manner of the ants," and

that indeed "its influence is always injurious to the seeds, even when

present only in excessively minute quantities." Though unable to explain

the method employed, he was convinced "that the non-germination of the

seeds is due to some direct influence voluntarily exercised by the ants,

and not merely to the conditions found in the nest" (page 172). See

Volume I., Letter 251.)

Down, February 21st [1873].

You have given me exactly the information which I wanted.

Geniuses jump. I have just procured formic acid to try whether its

vapour or minute drops will delay germination of fresh seeds; trying

others at same time for comparison. But I shall not be able to try them

till middle of April, as my despotic wife insists on taking a house in

London for a month from the middle of March.

I am glad to hear of the Primer (710/2. "Botany" (Macmillan's Science

Primers).); it is not at all, I think, a folly. Do you know Asa Gray's

child book on the functions of plants, or some such title? It is very

good in giving an interest to the subject.

By the way, can you lend me the January number of the "London Journal of

Botany" for an article on insect-agency in fertilisation?

LETTER 711. TO J. TRAHERNE MOGGRIDGE. Down, August 27th, 1873.

I thank you for your very interesting letter, and I honour you for your

laborious and careful experiments. No one knows till he tries how many

unexpected obstacles arise in subjecting plants to experiments.

I can think of no suggestions to make; but I may just mention that I

had intended to try the effects of touching the dampened seeds with the

minutest drop of formic acid at the end of a sharp glass rod, so as to

imitate the possible action of the sting of the ant. I heartily hope

that you may be rewarded by coming to some definite result; but I fail

five times out of six in my own experiments. I have lately been trying

some with poor success, and suppose that I have done too much, for I

have been completely knocked up for some days.

LETTER 712. TO J. TRAHERNE MOGGRIDGE. Down, March 10th, 1874.

I am very sorry to hear that the vapour experiments have failed; but

nothing could be better, as it seems to me, than your plan of enclosing

a number of the ants with the seeds. The incidental results on the power

of different vapours in killing seeds and stopping germination appear

very curious, and as far as I know are quite new.

P.S.--I never before heard of seeds not germinating except during a

certain season; it will be a very strange fact if you can prove this.

(712/1. Certain seeds pass through a resting period before germination.

See Pfeffer's "Pflanzenphysiologie," Edition I., Volume II., page III.)

LETTER 713. TO H. MULLER. Down, May 30th, 1873.

I am much obliged for your letter received this morning. I write now

chiefly to give myself the pleasure of telling you how cordially I

admire the last part of your book, which I have finished. (713/1.

"Die Befruchtung der Blumen durch Insekten": Leipzig, 1873. An English

translation was published in 1883 by Prof. D'Arcy Thompson. The

"Prefatory Notice" to this work (February 6th, 1882) is almost the last

of Mr. Darwin's writings. See "Life and Letters," page 281.) The whole

discussion seems to me quite excellent, and it has pleased me not a

little to find that in the rough MS. of my last chapter I have arrived

on many points at nearly the same conclusions that you have done, though

we have reached them by different routes. (713/2. "The Effects of Cross

and Self-Fertilisation in the Vegetable Kingdom": London, 1876.)

LETTER 714. TO F. DELPINO. Down, June 25th [1873].

I thank you sincerely for your letter. I am very glad to hear about

Lathyrus odoratus, for here in England the vars. never cross, and

yet are sometimes visited by bees. (714/1. In "Cross and

Self-Fertilisation," page 156, Darwin quotes the information received

from Delpino and referred to in the present letter--namely, that it

is the fixed opinion of the Italian gardeners that the varieties do

intercross. See Letter 709.) Pisum sativum I have also many times seen

visited by Bombus. I believe the cause of the many vars. not crossing

is that under our climate the flowers are self-fertilised at an early

period, before the corolla is fully expanded. I shall examine this point

with L. odoratus. I have read H. Muller's book, and it seems to me very

good. Your criticism had not occurred to me, but is, I think just--viz.

that it is much more important to know what insects habitually visit any

flower than the various kinds which occasionally visit it. Have you seen

A. Kerner's book "Schutzmittel des Pollens," 1873, Innsbruck. (714/2.

Afterwards translated by Dr. Ogle as "Flowers and their Unbidden

Guests," with a prefatory letter by Charles Darwin, 1878.) It is very

interesting, but he does not seem to know anything about the work of

other authors.

I have Bentham's paper in my house, but have not yet had time to read a

word of it. He is a man with very sound judgment, and fully admits the

principle of evolution.

I have lately had occasion to look over again your discussion on

anemophilous plants, and I have again felt much admiration at your work.

(714/3. "Atti della Soc. Italiana di Scienze Nat." Volume XIII.)

(714/4. In the beginning of August, 1873, Darwin paid the first of

several visits to Lord Farrer's house at Abinger. When sending copies of

Darwin's letters for the "Life and Letters," Lord Farrer was good enough

to add explanatory notes and recollections, from which we quote the

following sketch.)

"Above my house are some low hills, standing up in the valley, below the

chalk range on the one hand and the more distant range of Leith Hill

on the other, with pretty views of the valley towards Dorking in one

direction and Guildford in the other. They are composed of the less

fertile Greensand strata, and are covered with fern, broom, gorse, and

heath. Here it was a particular pleasure of his to wander, and his

tall figure, with his broad-brimmed Panama hat and long stick like an

alpenstock, sauntering solitary and slow over our favourite walks, is

one of the pleasantest of the many pleasant associations I have with the

place."

LETTER 715. TO T.H. FARRER (Lord Farrer).

(715/1. The following note by Lord Farrer explains the main point of

the letter, which, however, refers to the "bloom" problem as well as to

Coronilla:--

"I thought I had found out what puzzled us in Coronilla varia: in most

of the Papilionaceae, when the tenth stamen is free, there is nectar in

the staminal tube, and the opening caused by the free stamen enables the

bee to reach the nectar, and in so doing the bee fertilises the plant.

In Coronilla varia, and in several other species of Coronilla, there is

no nectar in the staminal tube or in the tube of the corolla. But

there are peculiar glands with nectar on the outside of the calyx, and

peculiar openings in the tube of the corolla through which the proboscis

of the bee, whilst entering the flower in the usual way and dusting

itself with pollen, can reach these glands, thus fertilising the plant

in getting the nectar. On writing this to Mr. Darwin, I received the

following characteristic note.

The first postscript relates to the rough ground behind my house, over

which he was fond of strolling. It had been ploughed up and then allowed

to go back, and the interest was to watch how the numerous species of

weeds of cultivation which followed the plough gradually gave way in the

struggle for existence to the well-known and much less varied flora of

an English common.")

Bassett, Southampton, August 14th, 1873.

You are the man to conquer a Coronilla. (715/2. In a former letter to

Lord Farrer, Darwin wrote: "Here is a maxim for you, 'It is disgraceful

to be beaten by a Coronilla.'") I have been looking at the half-dried

flowers, and am prepared to swear that you have solved the mystery.

The difference in the size of the cells on the calyx under the vexillum

right down to the common peduncle is conspicuous. The flour still

adhered to this side; I see little bracteae or stipules apparently with

glandular ends at the base of the calyces. Do these secrete? It seems

to me a beautiful case. When I saw the odd shape of the base of the

vexillum, I concluded that it must have some meaning, but little dreamt

what that was. Now there remains only the one serious point--viz.the

separation of the one stamen. I daresay that you are right in that

nectar was originally secreted within the staminal tube; but why has not

the one stamen long since cohered? The great difference in structure

for fertilisation within the same genus makes one believe that all such

points are vary variable. (715/3. Coronilla emerus is of the ordinary

papilionaceous type.) With respect to the non-coherence of the one

stamen, do examine some flower-buds at a very early age; for parts which

are largely developed are often developed to an unusual degree at a

very early age, and it seems to me quite possible that the base of the

vexillum (to which the single stamen adhered) might thus be developed,

and thus keep it separate for a time from the other stamens. The

cohering stamens to the right and left of the single one seem to me

to be pushed out a little laterally. When you have finished your

observations, you really ought to send an account with a diagram to

"Nature," recalling your generalisation about the diadelphous structure,

and now explaining the exception of Coronilla. (715/4. The observations

were published in "Nature," Volume X., 1874, page 169.)

Do add a remark how almost every detail of structure has a meaning where

a flower is well examined.

Your observations pleased me so much that I could not sit still for half

an hour.

Please to thank Mr. Payne (715/5. Lord Farrer's gardener.) for his

remarks, which are of value to me, with reference to Mimosa. I am

very much in doubt whether opening the sashes can act by favouring the

evaporation of the drops; may not the movement of the leaves shake off

the drops, or change their places? If Mr. Payne remembers any plant

which is easily injured by drops, I wish he would put a drop or two on

a leaf on a bright day, and cover the plant with a clean bell-glass,

and do the same for another plant, but without a bell-glass over it, and

observe the effects.

Thank you much for wishing to see us again at Abinger, and it is very

doubtful whether it will be Coronilla, Mr. Payne, the new garden, the

children, E. [Lady Farrer], or yourself which will give me the most

pleasure to see again.

P.S. 1.--It will be curious to note in how many years the rough ground

becomes quite uniform in its flora.

P.S. 2.--One may feel sure that periodically nectar was secreted within

the flower and then secreted by the calyx, as in some species of Iris

and orchids. This latter being taken advantage of in Coronilla would

allow of the secretion within the flower ceasing, and as this change was

going on in the two secretions, all the parts of the flower would become

modified and correlated.

LETTER 716. TO J. BURDON SANDERSON. Down, Tuesday, September 9th [1873].

(716/1. Sir J. Burdon Sanderson showed that in Dionoea movement

is accompanied by electric disturbances closely analogous to those

occurring in muscle (see "Nature," 1874, pages 105, 127; "Proc. R. Soc."

XXI., and "Phil. Trans." Volume CLXXIII., 1883, where the results are

finally discussed).)

I will send up early to-morrow two plants [of Dionoea] with five goodish

leaves, which you will know by their being tied to sticks. Please

remember that the slightest touch, even by a hair, of the three

filaments on each lobe makes the leaf close, and it will not open for

twenty-four hours. You had better put 1/4 in. of water into the saucers

of the pots. The plants have been kept too cool in order to retard

them. You had better keep them rather warm (i.e. temperature of warm

greenhouse) for a day, and in a good light.

I am extremely glad you have undertaken this subject. If you get a

positive result, I should think you ought to publish it separately, and

I could quote it; or I should be most glad to introduce any note by you

into my account.

I have no idea whether it is troublesome to try with the thermo-electric

pile any change of temperature when the leaf closes. I could detect none

with a common thermometer. But if there is any change of temperature I

should expect it would occur some eight to twelve or twenty-four

hours after the leaf has been given a big smashed fly, and when it is

copiously secreting its acid digestive fluid.

I forgot to say that, as far as I can make out, the inferior surface of

the leaf is always in a state of tension, and that the contraction is

confined to the upper surface; so that when this contraction ceases or

suddenly fails (as by immersion in boiling water) the leaf opens again,

or more widely than is natural to it.

Whenever you have quite finished, I will send for the plants in their

basket. My son Frank is staying at 6, Queen Anne Street, and comes home

on Saturday afternoon, but you will not have finished by that time.

P.S. I have repeated my experiment on digestion in Drosera with complete

success. By giving leaves a very little weak hydrochloric acid, I can

make them digest albumen--i.e. white of egg--quicker than they can do

naturally. I most heartily thank you for all your kindness. I have been

pretty bad lately, and must work very little.

LETTER 717. TO J. BURDON SANDERSON. September 13th [1873].

How very kind it was of you to telegraph to me. I am quite delighted

that you have got a decided result. Is it not a very remarkable fact? It

seems so to me, in my ignorance. I wish I could remember more distinctly

what I formerly read of Du Bois Raymond's results. My poor memory never

serves me for more than a vague guide. I really think you ought to try

Drosera. In a weak solution of phosphate of ammonia (viz. 1 gr. to 20

oz. of water) it will contract in about five minutes, and even more

quickly in pure warm water; but then water, I suppose, would prevent

your trial. I forget, but I think it contracts pretty quickly (i.e. in

an hour or two) with a large drop of a rather stronger solution of the

phosphate, or with an atom of raw meat on the disc of the leaf.

LETTER 718. TO J.D. HOOKER. October 31st, 1873.

Now I want to tell you, for my own pleasure, about the movements of

Desmodium.

1. When the plant goes to sleep, the terminal leaflets hang vertically

down, but the petioles move up towards the axis, so that the dependent

leaves are all crowded round it. The little leaflets never go to sleep,

and this seems to me very odd; they are at their games of play as late

as 11 o'clock at night and probably later. (718/1. Stahl ("Botanische

Zeitung," 1897, page 97) has suggested that the movements of the dwarf

leaflets in Desmodium serve to shake the large terminal leaflets, and

thus increase transpiration. According to Stahl's view their movement

would be more useful at night than by day, because stagnation of the

transpiration-current is more likely to occur at night.)

2. If the plant is shaken or syringed with tepid water, the terminal

leaflets move down through about an angle of 45 deg, and the petioles

likewise move about 11 deg downwards; so that they move in an opposite

direction to what they do when they go to sleep. Cold water or air

produces the same effect as does shaking. The little leaflets are not

in the least affected by the plant being shaken or syringed. I have no

doubt, from various facts, that the downward movement of the terminal

leaflets and petioles from shaking and syringing is to save them from

injury from warm rain.

3. The axis, the main petiole, and the terminal leaflets are all,

when the temperature is high, in constant movement, just like that of

climbing plants. This movement seems to be of no service, any more than

the incessant movement of amoeboid bodies. The movement of the terminal

leaflets, though insensible to the eye, is exactly the same as that of

the little lateral leaflets--viz. from side to side, up and down,

and half round their own axes. The only difference is that the little

leaflets move to a much greater extent, and perhaps more rapidly; and

they are excited into movement by warm water, which is not the case with

the terminal leaflet. Why the little leaflets, which are rudimentary in

size and have lost their sleep-movements and their movements from

being shaken, should not only have retained, but have their spontaneous

movements exaggerated, I cannot conceive. It is hardly credible that

it is a case of compensation. All this makes me very anxious to examine

some plant (if possible one of the Leguminosae) with either the terminal

or lateral leaflets greatly reduced in size, in comparison with the

other leaflets on the same leaf. Can you or any of your colleagues think

of any such plant? It is indirectly on this account that I so much want

the seeds of Lathyrus nissolia.

I hear from Frank that you think that the absence of both lateral

leaflets, or of one alone, is due to their having dropped off; I thought

so at first, and examined extremely young leaves from the tips of the

shoots, and some of them presented the same characters. Some appearances

make me think that they abort by becoming confluent with the main

petiole.

I hear also that you doubt about the little leaflets ever standing not

opposite to each other: pray look at the enclosed old leaf which

has been for a time in spirits, and can you call the little leaflets

opposite? I have seen many such cases on both my plants, though few so

well marked.

LETTER 719. TO J.D. HOOKER. Down, October 23rd [1873].

How good you have been about the plants; but indeed I did not intend

you to write about Drosophyllum, though I shall be very glad to have

a specimen. Experiments on other plants lead to fresh experiments.

Neptunia is evidently a hopeless case. I shall be very glad of the other

plants whenever they are ready. I constantly fear that I shall become to

you a giant of bores.

I am delighted to hear that you are at work on Nepenthes, and I hope

that you will have good luck. It is good news that the fluid is acid;

you ought to collect a good lot and have the acid analysed. I hope

that the work will give you as much pleasure as analogous work has me.

(719/1. Hooker's work on Nepenthes is referred to in "Insectivorous

Plants," page 97: see also his address at the Belfast meeting of the

British Association, 1874.) I do not think any discovery gave me more

pleasure than proving a true act of digestion in Drosera.

LETTER 720. TO J.D. HOOKER. Down, November 24th, 1873.

I have been greatly interested by Mimosa albida, on which I have been

working hard. Whilst your memory is pretty fresh, I want to ask a

question. When this plant was most sensitive, and you irritated it, did

the opposite leaflets shut up quite close, as occurs during sleep, when

even a lancet could not be inserted between the leaflets? I can never

cause the leaflets to come into contact, and some reasons make me doubt

whether they ever do so except during sleep; and this makes me wish much

to hear from you. I grieve to say that the plant looks more unhealthy,

even, than it was at Kew. I have nursed it like the tenderest infant;

but I was forced to cut off one leaf to try the bloom, and one was

broken by the manner of packing. I have never syringed (with tepid

water) more than one leaf per day; but if it dies, I shall feel like a

murderer. I am pretty well convinced that I shall make out my case of

movements as a protection against rain lodging on the leaves. As far as

I have as yet made out, M. albida is a splendid case.

I have had no time to examine more than one species of Eucalyptus. The

seedlings of Lathyrus nissolia are very interesting to me; and there is

something wonderful about them, unless seeds of two distinct leguminous

species have got somehow mingled together.

LETTER 721. TO W. THISELTON-DYER. Down, December 4th, 1873.

As Hooker is so busy, I should be very much obliged if you could give

me the name of the enclosed poor specimen of Cassia. I want much to

know its name, as its power of movement, when it goes to sleep, is very

remarkable. Linnaeus, I find, was aware of this. It twists each separate

leaflet almost completely round (721/1. See "Power of Movement in

Plants," Figure 154, page 370.), so that the lower surface faces the

sky, at the same time depressing them all. The terminal leaflets are

pointed towards the base of the leaf. The whole leaf is also raised

up about 12 deg. When I saw that it possessed such complex powers of

movement, I thought it would utilise its power to protect the leaflets

from rain. Accordingly I syringed the plant for two minutes, and it was

really beautiful to see how each leaflet on the younger leaves twisted

its short sub-petiole, so that the blade was immediately directed at

an angle between 45 and 90 deg to the horizon. I could not resist the

pleasure of just telling you why I want to know the name of the Cassia.

I should add that it is a greenhouse plant. I suppose that there will

not be any better flowers till next summer or autumn.

LETTER 722. TO T. BELT.

(722/1. Belt's account, discussed in this letter, is probably that

published in his "Naturalist in Nicaragua" (1874), where he describes

"the relation between the presence of honey-secreting glands on plants,

and the protection to the latter secured by the attendance of ants

attracted by the honey." (Op. cit., pages 222 et seq.))

Thursday [1874?].

Your account of the ants and their relations seems to me to possess

extraordinary interest. I do not doubt that the excretion of sweet fluid

by the glands is in your cases of great advantage to the plants by means

of the ants, but I cannot avoid believing that primordially it is a

simple excretion, as occasionally occurs from the surface of the leaves

of lime trees. It is quite possible that the primordial excretion may

have been beneficially increased to serve the plant. In the common

laurel [Prunus laurocerasus] of our gardens the hive-bees visit

incessantly the glands of the young leaves, on their under sides; and I

should altogether doubt whether their visits or the occasional visits of

ants was of any service to the laurel. The stipules of the common vetch

secrete largely during sunshine, and hive-bees collect the sweet fluid.

So I think it is with the common bean.

I am writing this away from home, and I have come away to get some rest,

having been a good deal overworked. I shall read your book with great

interest when published, but will not trouble you to send the MS., as I

really have no spare strength or time. I believe that your book, judging

by the chapter sent, will be extremely valuable.

LETTER 723. TO J.D. HOOKER.

(723/1. The following letter refers to Darwin's prediction as to the

manner in which Hedychium (Zinziberaceae) is fertilised. Sir J.D. Hooker

seems to have made inquiries in India in consequence of which

Darwin received specimens of the moth which there visits the flower,

unfortunately so much broken as to be useless (see "Life and Letters,"

III., page 284).)

Down, March 25th [1874].

I am glad to hear about the Hedychium, and how soon you have got an

answer! I hope that the wings of the Sphinx will hereafter prove to

be bedaubed with pollen, for the case will then prove a fine bit of

prophecy from the structure of a flower to special and new means of

fertilisation.

By the way, I suppose you have noticed what a grand appearance the plant

makes when the green capsules open, and display the orange and crimson

seeds and interior, so as to attract birds, like the pale buff flowers

to attract dusk-flying lepidoptera. I presume you do not want seeds of

this plant, as I have plenty from artificial fertilisation.

(723/2. In "Nature," June 22nd, 1876, page 173, Hermann Muller

communicated F. Muller's observation on the fertilisation of a

bright-red-flowered species of Hedychium, which is visited by

Callidryas, chiefly the males of C. Philea. The pollen is carried by the

tips of the butterfly's wing, to which it is temporarily fixed by the

slimy layer produced by the degeneration of the anther-wall.

LETTER 724. TO W. THISELTON-DYER. Down, June 4th [1874].

I am greatly obliged to you about the Opuntia, and shall be glad if you

can remember Catalpa. I wish some facts on the action of water, because

I have been so surprised at a stream not acting on Dionoea and Drosera.

(724/1. See Pfeffer, "Untersuchungen Bot. Inst. zu Tubingen," Bd.

I., 1885, page 518. Pfeffer shows that in some cases--Drosera, for

instance--water produces movement only when it contains fine particles

in suspension. According to Pfeffer the stamens of Berberis, and the

stigma of Mimulus, are both stimulated by gelatine, the action of which

is, generally speaking, equivalent to that of water.) Water does not

act on the stamens of Berberis, but it does on the stigma of Mimulus.

It causes the flowers of the bedding-out Mesembryanthemum and Drosera

to close, but it has not this effect on Gazania and the daisy, so I can

make out no rule.

I hope you are going on with Nepenthes; and if so, you will perhaps like

to hear that I have just found out that Pinguicula can digest albumen,

gelatine, etc. If a bit of glass or wood is placed on a leaf, the

secretion is not increased; but if an insect or animal-matter is thus

placed, the secretion is greatly increased and becomes feebly acid,

which was not the case before. I have been astonished and much disturbed

by finding that cabbage seeds excite a copious secretion, and am now

endeavouring to discover what this means. (724/2. Clearly it had not

occurred to Darwin that seeds may supply nitrogenous food as well as

insects: see "Insectivorous Plants," page 390.) Probably in a few days'

time I shall have to beg a little information from you, so I will write

no more now.

P.S. I heard from Asa Gray a week ago, and he tells me a beautiful fact:

not only does the lid of Sarracenia secrete a sweet fluid, but there

is a line or trail of sweet exudation down to the ground so as to tempt

insects up. (724/3. A dried specimen of Sarracenia, stuffed with cotton

wool, was sometimes brought from his study by Mr. Darwin, and made the

subject of a little lecture to visitors of natural history tastes.)

LETTER 725. TO W. THISELTON-DYER. Down, June 23rd, 1874.

I wrote to you about a week ago, thanking you for information on cabbage

seeds, asking you the name of Luzula or Carex, and on some other points;

and I hope before very long to receive an answer. You must now, if you

can, forgive me for being very troublesome, for I am in that state in

which I would sacrifice friend or foe. I have ascertained that bits

of certain leaves, for instance spinach, excite much secretion in

Pinguicula, and that the glands absorb matter from the leaves. Now this

morning I have received a lot of leaves from my future daughter-in-law

in North Wales, having a surprising number of captured insects on them,

a good many leaves, and two seed-capsules. She informs me that the

little leaves had excited secretion; and my son and I have ascertained

this morning that the protoplasm in the glands beneath the little leaves

has undoubtedly undergone aggregation. Therefore, absurd as it

may sound, I am prepared to affirm that Pinguicula is not only

insectivorous, but graminivorous, and granivorous! Now I want to beg you

to look under the simple microscope at the enclosed leaves and seeds,

and, if you possibly can, tell me their genera. The little narrow leaves

are remarkable (725/1. Those of Erica tetralix.); they are fleshy, with

the edges much curled from the axis of the plant, and bear a few long

glandular hairs; these grow in little tufts. These are the commonest in

Pinguicula, and seem to afford most nutritious matter. A second leaf is

like a miniature sycamore. With respect to the seeds, I suppose that

one is a Carex; the other looks like that of Rumex, but is enclosed in a

globular capsule. The Pinguicula grew on marshy, low, mountainous land.

I hope you will think this subject sufficiently interesting to make you

willing to aid me as far as you can. Anyhow, forgive me for being so

very troublesome.

LETTER 726. TO J.D. HOOKER. Down, August 30th [1874].

I am particularly obliged for your address. (726/1. Presidential address

(Biological Section) at the Belfast meeting of the British Association,

1874.) It strikes me as quite excellent, and has interested me in the

highest degree. Nor is this due to my having worked at the subject, for

I feel sure that I should have been just as much struck, perhaps more

so, if I had known nothing about it. You could not, in my opinion, have

put the case better. There are several lights (besides the facts) in

your essay new to me, and you have greatly honoured me. I heartily

congratulate you on so splendid a piece of work. There is a misprint at

page 7, Mitschke for Nitschke. There is a partial error at page 8, where

you say that Drosera is nearly indifferent to organic substances. This

is much too strong, though they do act less efficiently than organic

with soluble nitrogenous matter; but the chief difference is in the

widely different period of subsequent re-expansion. Thirdly, I did not

suggest to Sanderson his electrical experiments, though, no doubt, my

remarks led to his thinking of them.

Now for your letter: you are very generous about Dionoea, but some of

my experiments will require cutting off leaves, and therefore injuring

plants. I could not write to Lady Dorothy [Nevill]. Rollisson says that

they expect soon a lot from America. If Dionoea is not despatched, have

marked on address, "to be forwarded by foot-messenger."

Mrs. Barber's paper is very curious, and ought to be published (726/2.

Mrs. Barber's paper on the pupa of Papilio Nireus assuming different

tints corresponding to the objects to which it was attached, was

communicated by Mr. Darwin to the "Trans. Entomolog. Soc." 1874.); but

when you come here (and REMEMBER YOU OFFERED TO COME) we will consult

where to send it. Let me hear when you recommence on Cephalotus or

Sarracenia, as I think I am now on right track about Utricularia, after

wasting several weeks in fruitless trials and observations. The negative

work takes five times more time than the positive.

LETTER 727. TO J.D. HOOKER. Down, September 18th [1874].

I have had a splendid day's work, and must tell you about it.

Lady Dorothy sent me a young plant of U[tricularia] montana (727/1. See

"Life and Letters," III., page 327, and "Insectivorous Plants," page

431.), which I fancy is the species you told me of. The roots or

rhizomes (for I know not which they are; I can see no scales or

internodes or absorbent hairs) bear scores of bladders from 1/20 to

1/100 of an inch in diameter; and I traced these roots to the depth of 1

1/2 in. in the peat and sand. The bladders are like glass, and have the

same essential structure as those of our species, with the exception

that many exterior parts are aborted. Internally the structure is

perfect, as is the minute valvular opening into the bladder, which is

filled with water. I then felt sure that they captured subterranean

insects, and after a time I found two with decayed remnants, with clear

proof that something had been absorbed, which had generated protoplasm.

When you are here I shall be very curious to know whether they are roots

or rhizomes.

Besides the bladders there are great tuber-like swellings on the

rhizomes; one was an inch in length and half in breadth. I suppose

these must have been described. I strongly suspect that they serve as

reservoirs for water. (727/2. The existence of water-stores is quite

in accordance with the epiphytic habit of the plant.) But I shall

experimentise on this head. A thin slice is a beautiful object, and

looks like coarsely reticulated glass.

If you have an old plant which could be turned out of its pot (and can

spare the time), it would be a great gain to me if you would tear off a

bit of the roots near the bottom, and shake them well in water, and see

whether they bear these minute glass-like bladders. I should also much

like to know whether old plants bear the solid bladder-like bodies near

the upper surface of the pot. These bodies are evidently enlargements

of the roots or rhizomes. You must forgive this long letter, and

make allowance for my delight at finding this new sub-group of

insect-catchers. Sir E. Tennent speaks of an aquatic species of

Utricularia in Ceylon, which has bladders on its roots, and rises

annually to the surface, as he says, by this means. (727/3. Utricularia

stellaris. Emerson Tennent's "Ceylon," Volume I., page 124, 1859.)

We shall be delighted to see you here on the 26th; if you will let us

know your train we will send to meet you. You will have to work like a

slave while you are here.

LETTER 728. TO J. JENNER WEIR.

(728/1. In 1870 Mr. Jenner Weir wrote to Darwin: "My brother has but

two kinds of laburnum, viz., Cytisus purpureus, very erect, and Cytisus

alpinus, very pendulous. He has several stocks of the latter grafted

with the purple one; and this year, the grafts being two years old,

I saw in one, fairly above the stock, about four inches, a raceme of

purely yellow flowers with the usual dark markings, and above them a

bunch of purely purple flowers; the branches of the graft in no way

showed an intermediate character, but had the usual rigid growth of

purpureus."

Early in July 1875, when Darwin was correcting a new edition of

"Variation under Domestication," he again corresponded with Mr. Weir on

the subject.)

Down, July 8th [1875].

I thank you cordially. The case interests me in a higher degree than

anything which I have heard for a very long time. Is it your brother

Harrison W., whom I know? I should like to hear where the garden is.

There is one other very important point which I am most anxious to

hear--viz., the nature of the leaves at the base of the yellow racemes,

for leaves are always there produced with the yellow laburnums, and I

suppose so in the case of C. purpureus. As the tree has produced yellow

racemes several times, do you think you could ask your brother to cut

off and send me by post in a box a small branch of the purple stock with

the pods or leaves of the yellow sport? (728/2. "The purple stock" here

means the supposed C. purpureus, on which a yellow-flowered branch was

borne.) This would be an immense favour, for then I would cut the point

of junction longitudinally and examine slice under the microscope, to be

able to state no trace of bud of yellow kind having been inserted. I do

not suspect anything of the kind, but it is sure to be said that your

brother's gardener, either by accident or fraud, inserted a bud. Under

this point of view it would be very good to gather from your brother how

many times the yellow sport has appeared. The case appears to me so

very important as to be worth any trouble. Very many thanks for all

assistance so kindly given.

I will of course send a copy of new edition of "Variation under

Domestication" when published in the autumn.

LETTER 729. TO J. JENNER WEIR.

(729/1. On July 9th Mr. Weir wrote to say that a branch of the Cytisus

had been despatched to Down. The present letter was doubtless

written after Darwin had examined the specimen. In "Variation under

Domestication," Edition II., Volume I., page 417, note, he gives for a

case recorded in the "Gardeners' Chronicle" in 1857 the explanation here

offered (viz. that the graft was not C. purpureus but C. Adami), and

adds, "I have ascertained that this occurred in another instance." This

second instance is doubtless Mr. Weir's.)

Down, July 10th, 1875.

I do not know how to thank you enough; pray give also my thanks and kind

remembrances to your brother. I am sure you will forgive my expressing

my doubts freely, as I well know that you desire the truth more than

anything else. I cannot avoid the belief that some nurseryman has sold

C[ytisus] Adami to your brother in place of the true C. purpureus. The

latter is a little bush only 3 feet high (Loudon), and when I read your

account, it seemed to me a physical impossibility that a sporting branch

of C. alpinus could grow to any size and be supported on the extremely

delicate branches of C. purpureus. If I understand rightly your letter,

you consider the tuft of small shoots on one side of the sporting C.

alpinus from Weirleigh as C. purpureus; but these shoots are certainly

those of C. Adami. I earnestly beg you to look at the specimens

enclosed. The branch of the true C. purpureus is the largest which

I could find. If C. Adami was sold to your brother as C. purpureus,

everything is explained; for then the gardener has grafted C. Adami on

C. alpinus, and the former has sported in the usual manner; but has not

sported into C. purpureus, only into C. alpinus. C. Adami does not sport

less frequently into C. purpureus than into C. alpinus. Are the purple

flowers borne on moderately long racemes? If so, the plant is certainly

C. Adami, for the true C. purpureus bears flowers close to the branches.

I am very sorry to be so troublesome, but I am very anxious to hear

again from you.

C. purpureus bears "flowers axillary, solitary, stalked."

P.S.--I think you said that the purple [tree] at Weirleigh does not

seed, whereas the C. purpureus seeds freely, as you may see in enclosed.

C. Adami never produces seeds or pods.

LETTER 730. TO E. HACKEL.

(730/1. The following extract refers to Darwin's book on "Cross and

Self-Fertilisation.")

November 13th, 1875.

I am now busy in drawing up an account of ten years' experiments in the

growth and fertility of plants raised from crossed and self-fertilised

flowers. It is really wonderful what an effect pollen from a distinct

seedling plant, which has been exposed to different conditions of life,

has on the offspring in comparison with pollen from the same flower or

from a distinct individual, but which has been long subjected to the

same conditions. The subject bears on the very principle of life, which

seems almost to require changes in the conditions.

LETTER 731. TO G.J. ROMANES.

(731/1. The following extract from a letter to Romanes refers to Francis

Darwin's paper, "Experiments on the Nutrition of Drosera rotundifolia."

"Linn. Soc. Journ." [1878], published 1880, page 17.)

August 9th [1876].

The second point which delights me, seeing that half a score of

botanists throughout Europe have published that the digestion of meat by

plants is of no use to them (a mere pathological phenomenon, as one man

says!), is that Frank has been feeding under exactly similar conditions

a large number of plants of Drosera, and the effect is wonderful. On

the fed side the leaves are much larger, differently coloured, and more

numerous; flower-stalks taller and more numerous, and I believe far

more seed capsules,--but these not yet counted. It is particularly

interesting that the leaves fed on meat contain very many more starch

granules (no doubt owing to more protoplasm being first formed); so that

sections stained with iodine, of fed and unfed leaves, are to the naked

eye of very different colours.

There, I have boasted to my heart's content, and do you do the same, and

tell me what you have been doing.

LETTER 732. TO J.D. HOOKER. Down, October 25th [1876].

If you can put the following request into any one's hands pray do so;

but if not, ignore my request, as I know how busy you are.

I want any and all plants of Hoya examined to see if any imperfect

flowers like the one enclosed can be found, and if so to send them to

me, per post, damp. But I especially want them as young as possible.

They are very curious. I have examined some sent me from Abinger (732/1.

Lord Farrer's house.), but they were a month or two too old, and every

trace of pollen and anthers had disappeared or had never been developed.

Yet a very fine pod with apparently good seed had been formed by one

such flower. (732/2. The seeds did not germinate; see the account of

Hoya carnosa in "Forms of Flowers," page 331.)

LETTER 733. TO G.J. ROMANES.

(733/1. Published in the "Life of Romanes," page 62.)

Down, August 10th [1877].

When I went yesterday I had not received to-day's "Nature," and I

thought that your lecture was finished. (733/2. Abstract of a lecture

on "Evolution of Nerves and Nervo-Systems," delivered at the Royal

Institution, May 25th, 1877. "Nature," July 19th, August 2nd, August

9th, 1877.) This final part is one of the grandest essays which I ever

read.

It was very foolish of me to demur to your lines of conveyance like the

threads in muslin (733/3. "Nature," August 2nd, page 271.), knowing how

you have considered the subject: but still I must confess I cannot feel

quite easy. Everyone, I suppose, thinks on what he has himself seen, and

with Drosera, a bit of meat put on any one gland on its disc causes

all the surrounding tentacles to bend to this point, and here there can

hardly be differentiated lines of conveyance. It seems to me that the

tentacles probably bend to that point wherever a molecular wave strikes

them, which passes through the cellular tissue with equal ease in all

directions in this particular case. (733/4. Speaking generally, the

transmission takes place more readily in the longitudinal direction than

across the leaf: see "Insectivorous Plants," page 239.) But what a fine

case that of the Aurelia is! (733/5. Aurelia aurita, one of the medusae.

"Nature," pages 269-71.)

LETTER 734. TO W. THISELTON-DYER. 6, Queen Anne Street [December 1876].

Tell Hooker I feel greatly aggrieved by him: I went to the Royal Society

to see him for once in the chair of the Royal, to admire his dignity and

enjoy it, and lo and behold, he was not there. My outing gave me much

satisfaction, and I was particularly glad to see Mr. Bentham, and to see

him looking so wonderfully well and young. I saw lots of people, and it

has not done me a penny's worth of harm, though I could not get to sleep

till nearly four o'clock.

LETTER 735. TO D. OLIVER. Down, October, 13th [1876?].

You must be a clair-voyant or something of that kind to have sent me

such useful plants. Twenty-five years ago I described in my father's

garden two forms of Linum flavum (thinking it a case of mere variation);

from that day to this I have several times looked, but never saw the

second form till it arrived from Kew. Virtue is never its own reward:

I took paper this summer to write to you to ask you to send me flowers,

[so] that I might beg plants of this Linum, if you had the other form,

and refrained, from not wishing to trouble you. But I am now sorry

I did, for I have hardly any doubt that L. flavum never seeds in any

garden that I have seen, because one form alone is cultivated by slips.

(735/1. Id est, because, the plant being grown from slips, one form

alone usually occurs in any one garden. It is also arguable that it is

grown by slips because only one form is common, and therefore seedlings

cannot be raised.)

(736/1. The following five letters refer to Darwin's work on "bloom"--a

subject on which he did not live to complete his researches:--

One of his earliest letters on this subject was addressed in August,

1873, to Sir Joseph Hooker (736/2. Published in "Life and Letters,"

III., page 339.):

"I want a little information from you, and if you do not yourself know,

please to enquire of some of the wise men of Kew.

"Why are the leaves and fruit of so many plants protected by a thin

layer of waxy matter (like the common cabbage), or with fine hair, so

that when such leaves or fruit are immersed in water they appear as if

encased in thin glass? It is really a pretty sight to put a pod of the

common pea, or a raspberry, into water. I find several leaves are thus

protected on the under surface and not on the upper.

"How can water injure the leaves, if indeed this is at all the case?"

On this latter point Darwin wrote to the late Lord Farrer:

"I am now become mad about drops of water injuring leaves. Please ask

Mr. Payne (736/3. Lord Farrer's gardener.) whether he believes, FROM

HIS OWN EXPERIENCE, that drops of water injure leaves or fruit in his

conservatories. It is said that the drops act as burning-glasses; if

this is true, they would not be at all injurious on cloudy days. As

he is so acute a man, I should very much like to hear his opinion. I

remember when I grew hothouse orchids I was cautioned not to wet their

leaves; but I never then thought on the subject."

The next letter, though of later date than some which follow it, is

printed here because it briefly sums his results and serves as guide to

the letters dealing with the subject.)

LETTER 736. TO W. THISELTON-DYER.

(736/4. Published in "Life and Letters," III., page 341.)

Down, September 5th [1877].

One word to thank you. I declare, had it not been for your kindness,

we should have broken down. As it is we have made out clearly that with

some plants (chiefly succulent) the bloom checks evaporation--with

some certainly prevents attacks of insects; with SOME sea-shore plants

prevents injury from salt water, and, I believe, with a few prevents

injury from pure water resting on the leaves. This latter is as yet

the most doubtful and the most interesting point in relation to the

movements of plants.

(736/5. Modern research, especially that of Stahl on transpiration

("Bot. Zeitung," 1897, page 71) has shown that the question is more

complex than it appeared in 1877. Stahl's point of view is that moisture

remaining on a leaf checks the transpiration-current; and by thus

diminishing the flow of mineral nutriment interferes with the process of

assimilation. Stahl's idea is doubtless applicable to the whole problem

of bloom on leaves. For other references to bloom see letters 685, 689

and 693.)

LETTER 737. TO J.D. HOOKER. Down, August 19th, 1873.

The next time you walk round the garden ask Mr. Smith (737/1. Probably

John Smith (1798-1888), for some years Curator, Royal Gardens, Kew.), or

any of your best men, what they think about injury from watering during

sunshine. One of your men--viz., Mr. Payne, at Abinger, who seems very

acute--declares that you may water safely any plant out of doors in

sunshine, and that you may do the same for plants under glass if the

sashes are opened. This seems to me very odd, but he seems positive

on the point, and acts on it in raising splendid grapes. Another good

gardener maintains that it is only COLD water dripping often on the

same point of a leaf that ever injures it. I am utterly perplexed, but

interested on the point. Give me what you learn when you come to Down.

I should like to hear what plants are believed to be most injured by

being watered in sunshine, so that I might get such.

I expect that I shall be utterly beaten, as on so many other points;

but I intend to make a few experiments and observations. I have already

convinced myself that drops of water do NOT act as burning lenses.

LETTER 738. TO J.D. HOOKER. December 20th [1873].

I find that it is no use going on with my experiments on the evil

effects of water on bloom-divested leaves. Either I erred in the early

autumn or summer in some incomprehensible manner, or, as I suspect to be

the case, water is only injurious to leaves when there is a good supply

of actinic rays. I cannot believe that I am all in the wrong about the

movements of the leaves to shoot off water.

The upshot of all this is that I want to keep all the plants from Kew

until the spring or early summer, as it is mere waste of time going on

at present.

LETTER 739. TO W. THISELTON-DYER. Down, July 22nd [1877].

Many thanks for seeds of the Malva and information about Averrhoa, which

I perceived was sensitive, as A. carambola is said to be; and about

Mimosa sensitiva. The log-wood [Haematoxylon] has interested me much.

The wax is very easily removed, especially from the older leaves, and I

found after squirting on the leaves with water at 95 deg, all the older

leaves became coated, after forty-eight hours, in an astonishing manner

with a black Uredo, so that they looked as if sprinkled with soot and

water. But not one of the younger leaves was affected. This has set

me to work to see whether the "bloom" is not a protection against

parasites. As soon as I have ascertained a little more about the case

(and generally I am quite wrong at first) I will ask whether I could

have a very small plant, which should never be syringed with water above

60 deg, and then I suspect the leaves would not be spotted, as were the

older ones on the plant, when it arrived from Kew, but nothing like what

they were after my squirting.

In an old note of yours (which I have just found) you say that you have

a sensitive Schrankia: could this be lent me?

I have had lent me a young Coral-tree (Erythrina), which is very sickly,

yet shows odd sleep movements. I suppose I could buy one, but Hooker

told me first to ask you for anything.

Lastly, have you any seaside plants with bloom? I find that drops of

sea-water corrode sea-kale if bloom is removed; also the var. littorum

of Triticum repens. (By the way, my plants of the latter, grown in pots

here, are now throwing up long flexible green blades, and it is very odd

to see, ON THE SAME CULM, the rigid grey bloom-covered blades and the

green flexible ones.) Cabbages, ill-luck to them, do not seem to be

hurt by salt water. Hooker formerly told me that Salsola kali, a var. of

Salicornia, one species of Suaeda, Euphorbia peplis, Lathyrus maritimus,

Eryngium maritimum, were all glaucous and seaside plants. It is very

improbable that you have any of these or of foreigners with the same

attributes.

God forgive me: I hope that I have not bored you greatly.

By all the rules of right the leaves of the logwood ought to move (as if

partially going to sleep) when syringed with tepid water. The leaves

of my little plant do not move at all, and it occurs to me as possible,

though very improbable, that it would be different with a larger plant

with perhaps larger leaves. Would you some day get a gardener to syringe

violently, with water kept in a hothouse, a branch on one of your

largest logwood plants and observe [whether?] leaves move together

towards the apex of leaf?

By the way, what astonishing nonsense Mr. Andrew Murray has been

writing about leaves and carbonic acid! I like to see a man behaving

consistently...

What a lot I have scribbled to you!

(FIGURE 13. Leaf of Trifolium resupinatum (from a drawing by Miss

Pertz).)

LETTER 740. TO W. THISELTON-DYER. [August, 1877.]

There is no end to my requests. Can you spare me a good plant (or even

two) of Oxalis sensitiva? The one which I have (formerly from Kew) has

been so maltreated that I dare not trust my results any longer.

Please give the enclosed to Mr. Lynch. (740/1. Mr. Lynch, now Curator

of the Cambridge Botanic Garden, was at this time in the R. Bot. Garden,

Kew. Mr. Lynch described the movements of Averrhoa bilimbi in the "Linn.

Soc. Journ," Volume XVI., page 231. See also "The Power of Movement in

Plants," page 330.) The spontaneous movements of the Averrhoa are very

curious.

You sent me seeds of Trifolium resupinatum, and I have raised plants,

and some former observations which I did not dare to trust have proved

accurate. It is a very little fact, but curious. The half of the lateral

leaflets (marked by a cross) on the lower side have no bloom and are

wetted, whereas the other half has bloom and is not wetted, so that the

two sides look different to the naked eye. The cells of the eipdermis

appear of a different shape and size on the two sides of the leaf

[Figure 13].

When we have drawings and measurements of cells made, and are sure of

our facts, I shall ask you whether you know of any case of the same leaf

differing histologically on the two sides, for Hooker always says you

are a wonderful man for knowing what has been made out.

(740/2. The biological meaning of the curious structure of the leaves of

Trifolium resupinatum remains a riddle. The stomata and (speaking from

memory) the trichomes differ on the two halves of the lateral leaflets.)

LETTER 741. TO L. ERRERA.

(741/1. Professor L. Errera, of Brussels wrote, as a student, to Darwin,

asking permission to send the MS. of an essay by his friend S. Gevaert

and himself on cross and self-fertilisation, and which was afterwards

published in the "Bull. Soc. Bot. Belg." XVII., 1878. The terms

xenogamy, geitonogamy, and autogamy were first suggested by Kerner in

1876; their definition will be found at page 9 of Ogle's translation

of Kerner's "Flowers and their Unbidden Guests," 1878. In xenogamy the

pollen comes from another PLANT; in geitonogamy from another FLOWER

on the same PLANT; in autogamy from the androecium of the fertilised

FLOWER. Allogamy embraces xenogamy and geitonogamy.)

Down, October 4th, 1877.

I have now read your MS. The whole has interested me greatly, and

is very clearly written. I wish that I had used some such terms as

autogamy, xenogamy, etc...I entirely agree with you on the a priori

probability of geitonogamy being more advantageous than autogamy; and

I cannot remember having ever expressed a belief that autogamy, as a

general rule, was better than geitonogamy; but the cases recorded by

me seem too strong not to make me suspect that there was some unknown

advantage in autogamy. In one place I insert the caution "if this

be really the case," which you quote. (741/2. See "Cross and

Self-Fertilisation," pages 352, 386. The phrase referred to occurs in

both passages; that on page 386 is as follows: "We have also seen reason

to suspect that self-fertilisation is in some peculiar manner beneficial

to certain plants; but if this be really the case, the benefit thus

derived is far more than counterbalanced by a cross with a fresh stock

or with a slightly different variety." Errera and Gevaert conclude

(pages 79-80) that the balance of the available evidence is in favour of

the belief that geitonogamy is intermediate, in effectiveness, between

autogamy and xenogamy.) I shall be very glad to be proved to be

altogether in error on this point.

Accept my thanks for pointing out the bad erratum at page 301. I hope

that you will experimentise on inconspicuous flowers (741/3. See Miss

Bateson, "Annals of Botany," 1888, page 255, "On the Cross-Fertilisation

of Inconspicuous Flowers:" Miss Bateson showed that Senecio vulgaris

clearly profits by cross-fertilisation; Stellaria media and Capsella

bursa-pastoris less certainly.); if I were not too old and too much

occupied I would do so myself.

Finally let me thank you for the kind manner in which you refer to my

work, and with cordial good wishes for your success...

LETTER 742. TO W. THISELTON-DYER. Down, October 9th, 1877.

One line to thank you much about Mertensia. The former plant has begun

to make new leaves, to my great surprise, so that I shall be now well

supplied. We have worked so well with the Averrhoa that unless the

second species arrives in a very good state it would be superfluous to

send it. I am heartily glad that you and Mrs. Dyer are going to have

a holiday. I will look at you as a dead man for the next month, and

nothing shall tempt me to trouble you. But before you enter your grave

aid me if you can. I want seeds of three or four plants (not Leguminosae

or Cruciferae) which produce large cotyledons. I know not in the least

what plants have large cotyledons. Why I want to know is as follows: The

cotyledons of Cassia go to sleep, and are sensitive to a touch; but what

has surprised me much is that they are in constant movement up and down.

So it is with the cotyledons of the cabbage, and therefore I am very

curious to ascertain how far this is general.

LETTER 743. TO W. THISELTON-DYER. Down, October 11th [1877].

The fine lot of seeds arrived yesterday, and are all sown, and will be

most useful. If you remember, pray thank Mr. Lynch for his aid. I had

not thought of beech or sycamore, but they are now sown.

Perhaps you may like to see a rough copy of the tracing of movements

of one of the cotyledons of red cabbage, and you can throw it into

the fire. A line joining the two cotyledons stood facing a north-east

window, and the day was uniformly cloudy. A bristle was gummed to one

cotyledon, and beyond it a triangular bit of card was fixed, and in

front a vertical glass. A dot was made in the glass every quarter or

half hour at the point where the end of the bristle and the apex of card

coincided, and the dots were joined by straight lines. The observations

were from 10 a.m. to 8.45 p.m. During this time the enclosed figure was

described; but between 4 p.m. and 5.38 p.m. the cotyledon moved so that

the prolonged line was beyond the limits of the glass, and the course

is here shown by an imaginary dotted line. The cotyledon of Primula

sinensis moved in closely analogous manner, as do those of a Cassia.

Hence I expect to find such movements very general with cotyledons,

and I am inclined to look at them as the foundation for all the other

adaptive movements of leaves. They certainly are of the so-called sleep

of plants.

I hope I have not bothered you. Do not answer. I am all on fire at the

work.

I have had a short and very prosperous note from Asa Gray, who says

Hooker is very prosperous, and both are tremendously hard at work.

(743/1. "Hooker is coming over, and we are going in summer to the Rocky

Mountains together, according to an old promise of mine." Asa Gray to

G.F. Wright, May 24th, 1877 ("Letters of Asa Gray," II., page 666).)

LETTER 744. TO H. MULLER. Down, January 1st [1878?].

I must write two or three lines to thank you cordially for your very

handsome and very interesting review of my last book in "Kosmos,"

which I have this minute finished. (744/1. "Forms of Flowers," 1877. H.

Muller's article is in "Kosmos," II., page 286.) It is wonderful how you

have picked out everything important in it. I am especially glad that

you have called attention to the parallelism between illegitimate

offspring of heterostyled plants and hybrids. Your previous article in

"Kosmos" seemed to me very important, but for some unknown reason the

german was very difficult, and I was sadly overworked at the time, so

that I could not understand a good deal of it. (744/2. "Kosmos," II.,

pages 11, 128. See "Forms of Flowers," Edition II., page 308.) But I

have put it on one side, and when I have to prepare a new edition of my

book I must make it out. It seems that you attribute such cases as that

of the dioecious Rhamnus and your own of Valeriana to the existence of

two forms with larger and smaller flowers. I cannot follow the steps

by which such plants have been rendered dioecious, but when I read your

article with more care I hope I shall understand. (744/3. See "Forms of

Flowers," Edition II., pages 9 and 304. H. Muller's view is briefly that

conspicuous and less conspicuous varieties occurred, and that the former

were habitually visited first by insects; thus the less conspicuous form

would play the part of females and their pollen would tend to become

superfluous. See H. Muller in "Kosmos," II.) If you have succeeded

in explaining this class of cases I shall heartily rejoice, for they

utterly perplexed me, and I could not conjecture what their meaning was.

It is a grievous evil to have no faculty for new languages.

With the most sincere respect and hearty good wishes to you and all your

family for the new year...

P.S.--What interesting papers your wonderful brother has lately been

writing!

LETTER 745. TO W. THISELTON-DYER.

(745/1. This letter refers to the purchase of instruments for the

Jodrell Laboratory in the Royal Gardens, Kew. "The Royal Commission on

Scientific Instruction and the Advancement of Science, commonly spoken

of as the Devonshire Commission, in its fourth Report (1874), page 10,

expressed the opinion that 'it is highly desirable that opportunities

for the pursuit of investigations in Physiological Botany should be

afforded at Kew to those persons who may be inclined to follow that

branch of science.' Effect was given to this recommendation by the

liberality of the late T.J. Phillips-Jodrell, M.A., who built and

equipped the small laboratory, which has since borne his name, at his

own expense. It was completed and immediately brought into use in 1876."

The above is taken from the "Bulletin of Miscellaneous Information," R.

Botanic Gardens, Kew, 1901, page 102, which also gives a list of work

carried out in the laboratory between 1876 and 1900.)

Down, March 14th, 1878.

I have a very strong opinion that it would be the greatest possible

pity if the Phys[iological] Lab., now that it has been built, were

not supplied with as many good instruments as your funds can possibly

afford. It is quite possible that some of them may become antiquated

before they are much or even at all used. But this does not seem to me

any argument at all against getting them, for the Laboratory cannot be

used until well provided; and the mere fact of the instruments being

ready may suggest to some one to use them. You at Kew, as guardians and

promoters of botanical science, will then have done all in your power,

and if your Lab. is not used the disgrace will lie at the feet of the

public. But until bitter experience proves the contrary I will never

believe that we are so backward. I should think the German laboratories

would be very good guides as to what to get; but Timiriazeff of Moscow,

who travelled over Europe to see all Bot. Labs., and who seemed so

good a fellow, would, I should think, give the best list of the most

indispensable instruments. Lately I thought of getting Frank or

Horace to go to Cambridge for the use of the heliostat there; but our

observations turned out of less importance than I thought, yet if there

had been one at Kew we should probably have used it, and might have

found out something curious. It is impossible for me to predict whether

or not we should ever want this or that instrument, for we are guided

in our work by what turns up. Thus I am now observing something about

geotropism, and I had no idea a few weeks ago that this would have been

necessary. In a short time we might earnestly wish for a centrifugal

apparatus or a heliostat. In all such cases it would make a great

difference if a man knew that he could use a particular instrument

without great loss of time. I have now given my opinion, which is very

decided, whether right or wrong, and Frank quite agrees with me. You

can, of course, show this letter to Hooker.

LETTER 746. TO F. LUDWIG. Down, May 29th, 1878.

I thank you sincerely for the trouble which you have taken in sending

me so long and interesting a letter, together with the specimens.

Gradations are always very valuable, and you have been remarkably

successful in discovering the stages by which the Plantago has become

gyno-dioecious. (746/1. See F. Ludwig, "Zeitsch. f. d. Geo. Naturwiss."

Bd. LII., 1879. Professor Ludwig's observations are quoted in the

preface to "Forms of Flowers," Edition II., page ix.) Your view of its

origin, from being proterogynous, seems to me very probable, especially

as the females are generally the later-flowering plants. If you can

prove the reverse case with Thymus your view will manifestly be rendered

still more probable. I have never felt satisfied with H. Muller's view,

though he is so careful and admirable an observer. (746/2. See "Forms

of Flowers," Edition II., page 308. Also letter 744.) It is more than

seventeen years since I attended to Plantago, and when nothing had been

published on the subject, and in consequence I omitted to attend to

several points; and now, after so long an interval, I cannot pretend to

say to which of your forms the English one belongs; I well remember that

the anther of the females contained a good deal [of] pollen, though not

one sound grain.

P.S.--Delpino is Professor of Botany in Genoa, Italy (746/3. Now at

Naples.); I have always found him a most obliging correspondent.

LETTER 747. TO W. THISELTON-DYER. Down, August 24th [1878].

Many thanks for seeds of Trifolium resupinatum, which are invaluable to

us. I enclose seeds of a Cassia, from Fritz Muller, and they are well

worth your cultivation; for he says they come from a unique, large and

beautiful tree in the interior, and though looking out for years, he

has never seen another specimen. One of the most splendid, largest and

rarest butterflies in S. Brazil, he has never seen except near this

one tree, and he has just discovered that its caterpillars feed on its

leaves.

I have just been looking at fine young pods beneath the ground of

Arachis. (747/1. Arachis hypogoea, cultivated for its "ground nuts.") I

suppose that the pods are not withdrawn when ripe from the ground;

but should this be the case kindly inform me; if I do not hear I shall

understand that [the] pods ripen and are left permanently beneath the

ground.

If you ever come across heliotropic or apheliotropic aerial roots on

a plant not valuable (but which should be returned), I should like

to observe them. Bignonia capreolata, with its strongly apheliotropic

tendrils (which I had from Kew), is now interesting me greatly. Veitch

tells me it is not on sale in any London nursery, as I applied to him

for some additional plants. So much for business.

I have received from the Geographical Soc. your lecture, and read it

with great interest. (747/2. "On Plant-Distribution as a field for

Geographical Research." "Geog. Soc. Proc." XXII., 1878, page 412.) But

it ought not merely to be read; it requires study. The sole criticism

which I have to make is that parts are too much condensed: but, good

Lord, how rare a fault is this! You do not quote Saporta, I think; and

some of his work on the Tertiary plants would have been useful to you.

In a former note you spoke contemptuously of your lecture: all I can

say is that I never heard any one speak more unjustly and shamefully of

another than you have done of yourself!

LETTER 748. TO H. MULLER. Down, September 20th, 1878.

I am working away on some points in vegetable physiology, but though

they interest me and my son, yet they have none of the fascination which

the fertilisation of flowers possesses. Nothing in my life has ever

interested me more than the fertilisation of such plants as Primula and

Lythrum, or again Anacamptis (748/1. Orchis pyramidalis.) or Listera.

LETTER 749. TO H. MULLER. Down, February 12th [1879].

I have just heard that some misfortune has befallen you, and that you

have been treated shamefully. (749/1. Hermann Muller was accused by

the Ultramontane party of introducing into his school-teaching crude

hypotheses ("unreife Hypothesen"), which were assumed to have a harmful

influence upon the religious sentiments of his pupils. Attempts were

made to bring about Muller's dismissal, but the active hostility of his

opponents, which he met in a dignified spirit, proved futile. ("Prof.

Dr. Hermann Muller von Lippstadt. Ein Gedenkblatt," von Ernst Krause.

"Kosmos," VII., page 393, 1883.)) I grieve deeply to hear this, and as

soon as you can find a few minutes to spare, I earnestly beg you to let

me hear what has happened.

LETTER 750. TO A. STEPHEN WILSON.

(750/1. The following letters refer to two forms of wheat cultivated in

Russia under the names Kubanka and Saxonka, which had been sent to Mr.

Darwin by Dr. Asher from Samara, and were placed in the hands of Mr.

Wilson that he might test the belief prevalent in Russia that Kubanka

"grown repeatedly on inferior soil," assumes "the form of Saxonka." Mr.

Wilson's paper of 1880 gives the results of his inquiry. He concludes

(basing his views partly on analogous cases and partly on his study of

the Russian wheats) that the supposed transformation is explicable in

chief part by the greater fertility of the Saxonka wheat leading to

extermination of the other form. According to Mr. Wilson, therefore,

the Saxonka survivors are incorrectly assumed to be the result of the

conversion of one form into the other.)

Down, April 24th, 1878.

I send you herewith some specimens which may perhaps interest you, as

you have so carefully studied the varieties of wheat. Anyhow, they are

of no use to me, as I have neither knowledge nor time sufficient. They

were sent me by the Governor of the Province of Samara, in Russia, at

the request of Dr. Asher (son of the great Berlin publisher) who farmed

for some years in the province. The specimen marked Kubanka is a very

valuable kind, but which keeps true only when cultivated in fresh

steppe-land in Samara, and in Saratoff. After two years it degenerates

into the variety Saxonica, or its synonym Ghirca. The latter alone is

imported into this country. Dr. Asher says that it is universally known,

and he has himself witnessed the fact, that if grain of the Kubanka is

sown in the same steppe-land for more than two years it changes into

Saxonica. He has seen a field with parts still Kubanka and the remainder

Saxonica. On this account the Government, in letting steppe-land,

contracts that after two years wheat must not be sown until an interval

of eight years. The ears of the two kinds appear different, as you will

see, but the chief difference is in the quality of the grains. Dr. Asher

has witnessed sales of equal weights of Kubanka and Saxonica grain,

and the price of the former was to that of the latter as 7 to 4. The

peasants say that the change commences in the terminal grain of the

ear. The most remarkable point, as Dr. Asher positively asserts, is that

there are no intermediate varieties; but that a grain produces a plant

yielding either true Kubanka or true Saxonica. He thinks that it would

be interesting to sow here both kinds in good and bad wheat soil and

observe the result. Should you think it worth while to make any such

trial, and should you require further information, Dr. Asher, whose

address I enclose, will be happy to give any in his power.

LETTER 751. TO A. STEPHEN WILSON. Basset, Southampton, April 29th

[1878].

Your kind note and specimens have been forwarded to me here, where I

am staying at my son's house for a fortnight's complete rest, which

I required from rather too hard work. For this reason I will not now

examine the seeds, but will wait till returning home, when, with my son

Francis' aid, I will look to them.

I always felt, though without any good reason, rather sceptical about

Prof. Buckman's experiment, and I afterwards heard that a most wicked

and cruel trick had been played on him by some of the agricultural

students at Cirencester, who had sown seeds unknown to him in his

experimental beds. Whether he ever knew this I did not hear.

I am exceedingly glad that you are willing to look into the Russian

wheat case. It may turn out a mare's nest, but I have often incidentally

observed curious facts when making what I call "a fool's experiment."

LETTER 752. TO A. STEPHEN WILSON. Down, March 5th, 1879.

I have just returned home after an absence of a week, and your letter

was not forwarded to me; I mention this to account for my apparent

discourtesy in not having sooner thanked you. You have worked out

the subject with admirable care and clearness, and your drawings are

beautiful. I suspected that there was some error in the Russian belief,

but I did not think of the explanation which you have almost proved

to be the true one. It is an extremely interesting instance of a more

fertile variety beating out a less fertile one, and, in this case, one

much more valuable to man. With respect to publication, I am at a

loss to advise you, for I live a secluded life and do not see many

periodicals, or hear what is done at the various societies. It seems to

me that your paper should be published in some agricultural journal; for

it is not simply scientific, and would therefore not be published by the

Linnean or Royal Societies.

Would the Royal Agricultural Society be a fitting place? Unfortunately

I am not a member, and could not myself present it. Unless you think

of some better journal, there is the "Agricultural Gazette": I have

occasionally suggested articles for publication to the editor (though

personally unknown to me) which he has always accepted.

Permit me again to thank you for the thorough manner in which you have

worked out this case; to kill an error is as good a service as, and

sometimes even better than, the establishing a new truth or fact.

LETTER 753. TO A. STEPHEN WILSON. Down, February 13th, 1880.

It was very kind of you to send me two numbers of the "Gardeners'

Chronicle" with your two articles, which I have read with much interest.

(753/1. "Gardeners' Chronicle," 1879, page 652; 1880, pages 108, 173.)

You have quite convinced me, whatever Mr. Asher may say to the contrary.

I want to ask you a question, on the bare chance of your being able to

answer it, but if you cannot, please do not take the trouble to write.

The lateral branches of the silver fir often grow out into knobs through

the action of a fungus, Aecidium; and from these knobs shoots grow

vertically (753/2. The well-known "Witches-Brooms," or "Hexen-Besen,"

produced by the fungus Aecidium elatinum.) instead of horizontally, like

all the other twigs on the same branch. Now the roots of Cruciferae and

probably other plants are said to become knobbed through the action of

a fungus: now, do these knobs give rise to rootlets? and, if so, do they

grow in a new or abnormal direction? (753/3. The parasite is probably

Plasmodiophora: in this case no abnormal rootlets have been observed, as

far as we know.)

LETTER 754. TO W. THISELTON-DYER. Down, June 18th, 1879.

The plants arrived last night in first-rate order, and it was very very

good of you to take so much trouble as to hunt them up yourself. They

seem exactly what I wanted, and if I fail it will not be for want of

perfect materials. But a confounded painter (I beg his pardon) comes

here to-night, and for the next two days I shall be half dead with

sitting to him; but after then I will begin to work at the plants and

see what I can do, and very curious I am about the results.

I have to thank you for two very interesting letters. I am delighted

to hear, and with surprise, that you care about old Erasmus D. God only

knows what I shall make of his life--it is such new kind of work to me.

(754/1. "Erasmus Darwin." By Ernst Krause. Translated from the German by

W.S. Dallas: with a preliminary notice by Charles Darwin. London, 1879.

See "Life and Letters," III., pages 218-20.)