foregoing cases may be looked at as the direct result of the inoculation of
a disease or some weakness. This has been almost proved to be the case by
Morren in the excellent paper just referred to, who shows that even a leaf
inserted by its footstalk into the bark of the stock is sufficient to
communicate variegation to it, though the leaf soon perishes. Even fully
formed leaves on the stock of Abutilon are sometimes affected by the graft
and become variegated. Variegation is much influenced, as we shall
hereafter see, by the nature of the soil in which the plants are grown; and
it does not seem improbable that whatever change in the sap or tissues
certain soils induce, whether or not called a disease, might spread from
the inserted piece of bark to the stock. But a change of this kind cannot
be considered to be of the nature of a graft-hybrid.
There is a variety of the hazel with dark-purple leaves, like those of the
copper-beech: no one has attributed this colour to disease, and it
apparently is only an exaggeration of a tint which may often be seen on the
leaves of the common hazel. When this variety is grafted on the common
hazel (11/105. Loudon's 'Arboretum' volume 4 page 2595.), it sometimes
colours, as has been asserted, the leaves below the graft; although
negative evidence is not of much value, I may add that Mr. Rivers, who has
possessed hundreds of such grafted trees, has never seen an instance.
Gartner (11/106. 'Bastarderzeugung' s. 619.) quotes two separate accounts
of branches of dark and white-fruited vines which had been united in
various ways, such as being split longitudinally, and then joined, etc.;
and these branches produced distinct bunches of grapes of the two colours,
and other bunches with berries, either striped, or of an intermediate and
new tint. Even the leaves in one case were variegated. These facts are the
more remarkable because Andrew Knight never succeeded in raising variegated
grapes by fertilising white kinds by pollen of dark kinds; though, as we
have seen, he obtained seedlings with variegated fruits and leaves, by
fertilising a white variety by the already variegated dark Aleppo grape.
Gartner attributes the above-quoted cases merely to bud-variation; but it
is a strange coincidence that the branches which had been grafted in a
peculiar manner should alone thus have varied; and H. Adorne de Tscharner
positively asserts that he produced the described result more than once,
and could do so at will, by splitting and uniting the branches in the
manner described by him.
I should not have quoted the following case had not the author of 'Des
Jacinthes' (11/107. Amsterdam 1768 page 124.) impressed me with the belief
not only of his extensive knowledge, but of his truthfulness: he says that
bulbs of blue and red hyacinths may be cut in two, and that they will grow
together and throw up a united stem (and this I have myself seen) with
flowers of the two colours on the opposite sides. But the remarkable point
is, that flowers are sometimes produced with the two colours blended
together, which makes the case closely analogous with that of the blended
colours of the grapes on the united vine branches.
In the case of roses it is supposed that several graft-hybrids have been
formed, but there is much doubt about these cases, owing to the frequency
of ordinary bud-variations. The most trustworthy instance known to me is
one, recorded by Mr. Poynter (11/108. 'Gardener's Chron.' 1860 page 672
with a woodcut.) who assures me in a letter of the entire accuracy of the
statement. Rosa devoniensis had been budded some years previously on a
white Banksian rose; and from the much enlarged point of junction, whence
the Devoniensis and Banksian still continued to grow, a third branch
issued, which was neither pure Banksian nor pure Devoniensis, but partook
of the character of both; the flowers resembled, but were superior in
character to those of the variety called Lamarque (one of the Noisettes),
while the shoots were similar in their manner of growth to those of the
Banksian rose, with the exception that the longer and more robust shoots
were furnished with prickles. This rose was exhibited before the Floral
Committee of the Horticultural Society of London. Dr. Lindley examined it
and concluded that it had certainly been produced by the mingling of R.
banksiae with some rose like R. devoniensis, "for while it was very greatly
increased in vigour and in size of all the parts, the leaves were half-way
between a Banksian and Tea-scented rose." It appears that rose-growers were
previously aware that the Banksian rose sometimes affects other roses. As
Mr. Poynter's new variety is intermediate in its fruit and foliage between
the stock and scion, and as it arose from the point of junction between the
two, it is very improbable that it owes its origin to mere bud-variation,
independently of the mutual influence of the stock and scion.
Lastly, with respect to potatoes. Mr. R. Trail stated in 1867 before the
Botanical Society of Edinburgh (and has since given me fuller information),
that several years ago he cut about sixty blue and white potatoes into
halves through the eyes or buds, and then carefully joined them, destroying
at the same time the other eyes. Some of these united tubers produced
white, and others blue tubers; some, however, produced tubers partly white
and partly blue; and the tubers from about four or five were regularly
mottled with the two colours. In these latter cases we may conclude that a
stem had been formed by the union of the bisected buds, that is, by graft-
hybridisation.
In the 'Botanische Zeitung' (May 16, 1868), Professor Hildebrand gives an
account with a coloured figure, of his experiments on two varieties which
were found during the same season to be constant in character, namely, a
somewhat elongated rough-skinned red potato and a rounded smooth white one.
He inserted buds reciprocally into both kinds, destroying the other buds.
He thus raised two plants, and each of these produced a tuber intermediate
in character between the two parent-forms. That from the red bud grafted
into the white tuber, was at one end red and rough, as the whole tuber
ought to have been if not affected; in the middle it was smooth with red
stripes, and at the other end smooth and altogether white like that of the
stock.
Mr. Taylor, who had received several accounts of potatoes having been
grafted by wedge-shaped pieces of one variety inserted into another, though
sceptical on the subject, made twenty-four experiments which he described
in detail before the Horticultural Society. (11/109. 'Gardener's Chronicle'
1869 page 220.) He thus raised many new varieties, some like the graft or
like the stock; others having an intermediate character. Several persons
witnessed the digging up of the tubers from these graft-hybrids; and one of
them, Mr. Jameson, a large dealer in potatoes, writes thus, "They were such
a mixed lot, as I have never before or since seen. They were of all colours
and shapes, some very ugly and some very handsome." Another witness says
"some were round, some kidney, pink-eyed kidney, piebald, and mottled red
and purple, of all shapes and sizes." Some of these varieties have been
found valuable, and have been extensively propagated. Mr. Jameson took away
a large piebald potato which he cut into five sets and propagated; these
yielded round, white, red, and piebald potatoes.
Mr. Fitzpatrick followed a different plan (11/110. 'Gard. Chronicle' 1869
page 335.); he grafted together not the tubers but the young stems of
varieties producing black, white, and red potatoes. The tubers borne by
three of these twin or united plants were coloured in an extraordinary
manner; one was almost exactly half black and half white, so that some
persons on seeing it thought that two potatoes had been divided and
rejoined; other tubers were half red and half white, or curiously mottled
with red and white, or with red and black, according to the colours of the
graft and stock.
The testimony of Mr. Fenn is of much value, as he is "a well known potato-
grower" who has raised many new varieties by crossing different kinds in
the ordinary manner. He considers it "demonstrated" that new, intermediate
varieties can be produced by grafting the tubers, though he doubts whether
such will prove valuable. (11/111. 'Gardener's Chronicle' 1869 page 1018
with remarks by Dr. Masters on the adhesion of the united wedges. See also
ibid 1870 pages 1277, 1283.) He made many trials and laid the results,
exhibiting specimens, before the Horticultural Society. Not only were the
tubers affected, some being smooth and white at one end and rough and red
at the other, but the stems and leaves were modified in their manner of
growth, colour and precocity. Some of these graft-hybrids after being
propagated for three years still showed in their haulms their new
character, different from that of the kind from which the eyes had been
taken. Mr. Fenn gave twelve of the tubers of the third generation to Mr.
Alex. Dean, who grew them, and was thus converted into a believer in graft-
hybridisation, having previously been a complete sceptic. For comparison he
planted the pure parent-forms alongside the twelve tubers; and found that
many of the plants from the latter (11/112. 'Gard. Chronicle' 1871 page
837.) were intermediate between the two parent-forms in precocity, in the
tallness, uprightness, jointing, and robustness of the stems, and in the
size and colour of the leaves.
Another experimentalist, Mr. Rintoul, grafted no less than fifty-nine
tubers, which differed in shape (some being kidneys) in smoothness and
colour (11/113. 'Gardener's Chronicle' 1870 page 1506.) and many of the
plants thus raised "were intermediate in the tubers as well as in the
haulms." He describes the more striking cases.
In 1871 I received a letter from Mr. Merrick, of Boston, U.S.A., who states
that, "Mr. Fearing Burr, a very careful experimenter and author of a much
valued book, 'The Garden Vegetables of America' has succeeded in producing
distinctly mottled and most curious potatoes--evidently graft-hybrids, by
inserting eyes from blue or red potatoes into the substance of white ones,
after removing the eyes of the latter. I have seen the potatoes, and they
are very curious."
We will now turn to the experiments made in Germany, since the publication
of Prof. Hildebrand's paper. Herr Magnus relates (11/114. 'Sitzungsberichte
der Gesellschaft naturforschender Freunde zu Berlin' October 17, 1871.) the
results of numerous trials made by Herren Reuter and Lindemuth, both
attached to the Royal Gardens of Berlin. They inserted the eyes of red
potatoes into white ones, and vice versa. Many different forms partaking of
the characters of the inserted bud and of the stock were thus obtained; for
instance, some of the tubers were white with red eyes.
Herr Magnus also exhibited in the following year before the same Society
(November 19, 1872), the produce of grafts between black, white, and red
potatoes, made by Dr. Neubert. These were made by uniting not the tubers
but the young stems, as was done by Mr. Fitzpatrick. The result was
remarkable, inasmuch as all the tubers thus produced were intermediate in
character, though in a variable degree. Those between the black and the
white or the red were the most striking in appearance. Some from between
the white and red had one half of one colour and the other half of the
other colour.
At the next meeting of the society Herr Magnus communicated the results of
Dr. Heimann's experiments in grafting together the tubers of red Saxon,
blue, and elongated white potatoes. The eyes were removed by a cylindrical
instrument, and inserted into corresponding holes in other varieties. The
plants thus produced yielded a great number of tubers, which were
intermediate between the two parent-forms in shape, and in the colour both
of the flesh and skin.
Herr Reuter experimented (11/115. Ibid November 17, 1874. See also
excellent remarks by Herr Magnus.) by inserting wedges of the elongated
White Mexican potato into a Black Kidney potato. Both sorts are known to be
very constant, and differ much not only in form and colour, but in the eyes
of the Black Kidney being deeply sunk, whereas those of the White Mexican
are superficial and of a different shape. The tubers produced by these
hybrids were intermediate in colour and form; and some which resembled in
form the graft, i.e. the Mexican, had eyes deeply sunk and of the same
shape as in the stock or Black Kidney.]
Any one who will attentively consider the abstract now given, of the
experiments made by many observers in several countries, will, I think, be
convinced that by grafting two varieties of the potato together in various
ways, hybridised plants can be produced. It should be observed that several
of the experimentalists are scientific horticulturists, and some of them
potato-growers on a large scale, who, though beforehand sceptical, have
been fully convinced of the possibility, even of the ease, of making graft-
hybrids. The only way of escaping from this conclusion is to attribute all
the many recorded cases to simple bud-variation. Undoubtedly the potato, as
we have seen in this chapter, does sometimes, though not often, vary by
buds; but it should be especially noted that it is experienced potato-
growers, whose business it is to look out for new varieties, who have
expressed unbounded astonishment at the number of new forms produced by
graft-hybridisation. It may be argued that it is merely the operation of
grafting, and not the union of two kinds, which causes so extraordinary an
amount of bud-variation; but this objection is at once answered by the fact
that potatoes are habitually propagated by the tubers being cut into
pieces, and the sole difference in the case of graft-hybrids is that either
a half or a smaller segment or a cylinder is placed in close opposition
with the tissue of another variety. Moreover, in two cases, the young stems
were grafted together, and the plants thus united yielded the same results
as when the tubers were united. It is an argument of the greatest weight
that when varieties are produced by simple bud-variation, they frequently
present quite new characters; whereas in all the numerous cases above
given, as Herr Magnus likewise insists, the graft-hybrids are intermediate
in character between the two forms employed. That such a result should
follow if the one kind did not affect the other is incredible.
Characters of all kinds are affected by graft hybridisation, in whatever
way the grafting may have been effected. The plants thus raised yield
tubers which partake of the widely different colours, form, state of
surface, position and shape of the eye of the parents; and according to two
careful observers they are also intermediate in certain constitutional
peculiarities. But we should bear in mind that in all the varieties of the
potato, the tubers differ much more than any other part.
The potato affords the best evidence of the possibility of the formation of
graft-hybrids, but we must not overlook the account given of the origin of
the famous Cytisus adami by M. Adam, who had no conceivable motive for
deception, and the exactly parallel account of the origin of the Bizzarria
orange, namely by graft-hybridisation. Nor must the cases be undervalued in
which different varieties or species of vines, hyacinths and roses, have
been grafted together, and have yielded intermediate forms. It is evident
that graft-hybrids can be made much more easily with some plants, as the
potato, than with others, for instance our common fruit trees; for these
latter have been grafted by the million during many centuries, and though
the graft is often slightly affected, it is very doubtful whether this may
not be accounted for, merely by a more or less free supply of nutriment.
Nevertheless, the cases above given seem to me to prove that under certain
unknown conditions graft-hybridisation can be effected.
Herr Magnus asserts with much truth that graft-hybrids resemble in all
respects seminal hybrids, including their great diversity of character.
There is, however, a partial exception, inasmuch as the characters of the
two parent forms are not often homogeneously blended together in graft-
hybrids. They much more commonly appear in a segregated condition,--that
is, in segments either at first, or subsequently through reversion. It
would seem that the reproductive elements are not so completely blended by
grafting as by sexual generation. But segregation of this kind occurs by no
means rarely, as will be immediately shown, in seminal hybrids. Finally it
must, I think, be admitted that we learn from the foregoing cases a highly
important physiological fact, namely, that the elements that go to the
production of a new being, are not necessarily formed by the male and
female organs. They are present in the cellular tissue in such a state that
they can unite without the aid of the sexual organs, and thus give rise to
a new bud partaking of the characters of the two parent-forms.
ON THE SEGREGATION OF THE PARENTAL CHARACTERS IN SEMINAL HYBRIDS BY BUD-
VARIATION.
I will now give a sufficient number of cases to show that segregation of
this kind, namely, by buds, may occur in ordinary hybrids raised from seed.
[Hybrids were raised by Gartner between Tropaeolum minus and majus (11/116.
'Bastarderzeugung' s. 549. It is, however, doubtful whether these plants
should be ranked as species or varieties.) which at first produced flowers
intermediate in size, colour, and structure between their two parents; but
later in the season some of these plants produced flowers in all respects
like those of the mother-form, mingled with flowers still retaining the
usual intermediate condition. A hybrid Cereus between C. speciosissimus and
phyllanthus (11/117. Gartner ibid s. 550.) plants which are widely
different in appearance, produced for the first three years angular, five-
sided stems, and then some flat stems like those of C. phyllanthus.
Kolreuter also gives cases of hybrid Lobelias and Verbascums, which at
first produced flowers of one colour, and later in the season, flowers of a
different colour. (11/118. 'Journal de Physique' tome 23 1873 page 100.
'Act. Acad. St. Petersburgh' 1781 part 1 page 249.) Naudin (11/119.
'Nouvelles Archives du Museum' tome 1 page 49.) raised forty hybrids from
Datura laevis fertilised by D. stramonium; and three of these hybrids
produced many capsules, of which a half, or quarter, or lesser segment was
smooth and of small size, like the capsule of the pure D. laevis, the
remaining part being spinose and of larger size, like the capsule of the
pure D. stramonium: from one of these composite capsules, plants perfectly
resembling both parent-forms were raised.
Turning now to varieties. A SEEDLING apple, conjectured to be of crossed
parentage, has been described in France (11/120. L'Hermes January 14, 1837
quoted in Loudon's 'Gardener's Mag.' volume 13 page 230.) which bears fruit
with one half larger than the other, of a red colour, acid taste, and
peculiar odour; the other side being greenish-yellow and very sweet: it is
said scarcely ever to include perfectly developed seed. I suppose that this
is not the same tree as that which Gaudichaud (11/121. 'Comptes Rendus'
tome 34 1852 page 746.) exhibited before the French institute, bearing on
the same branch two distinct kinds of apples, one a reinette rouge, and the
other like a reinette canada jaunatre: this double-bearing variety can be
propagated by grafts, and continues to produce both kinds; its origin is
unknown. The Rev. J.D. La Touche sent me a coloured drawing of an apple
which he brought from Canada, of which half, surrounding and including the
whole of the calyx and the insertion of the foot-stalk, is green, the other
half being brown and of the nature of the pomme gris apple, with the line
of separation between the two halves exactly defined. The tree was a
grafted one, and Mr. La Touche thinks that the branches which bore this
curious apple sprung from the point of junction of the graft and stock: had
this fact been ascertained, the case would probably have come into the
class of graft-hybrids already given. But the branch may have sprung from
the stock, which no doubt was a seedling.
Prof. H. Lecoq, who has made a great number of crossings between the
differently coloured varieties of Mirabilis jalapa (11/122. 'Geograph. Bot.
de l'Europe' tome 3 1854 page 405; and 'De la Fecondation' 1862 page 302.)
finds that in the seedlings the colours rarely combine, but form distinct
stripes; or half the flower is of one colour and half of a different
colour. Some varieties regularly bear flowers striped with yellow, white,
and red; but plants of such varieties occasionally produce on the same root
branches with uniformly coloured flowers of all three tints, and other
branches with half-and-half coloured flowers, and others with marbled
flowers. Gallesio (11/123. 'Traite du Citrus' 1811 page 45.) crossed
reciprocally white and red carnations, and the seedlings were striped; but
some of the striped plants also bore entirely white and entirely red
flowers. Some of these plants produced one year red flowers alone, and in
the following year striped flowers; or conversely, some plants, after
having borne for two or three years striped flowers, would revert and bear
exclusively red flowers. It may be worth mentioning that I fertilised the
PURPLE SWEET-PEA (Lathyrus odoratus) with pollen from the light-coloured
PAINTED LADY: seedlings raised from the same pod were not intermediate in
character, but perfectly resembled either parent. Later in the summer, the
plants which had at first borne flowers identical with those of the PAINTED
LADY, produced flowers streaked and blotched with purple; showing in these
darker marks a tendency to reversion to the mother-variety. Andrew Knight
(11/124. 'Transact. Linn. Soc.' volume 9 page 268.) fertilised two white
grapes with pollen of the Aleppo grape, which is darkly variegated both in
its leaves and fruit. The result was that the young seedlings were not at
first variegated, but all became variegated during the succeeding summer;
besides this, many produced on the same plant bunches of grapes which were
all black, or all white, or lead-coloured striped with white, or white
dotted with minute black stripes; and grapes of all these shades could
frequently be found on the same foot-stalk.
I will append a very curious case, not of bud-variation, but of two
cohering embryos, different in character and contained within the same
seed. A distinguished botanist, Mr. G.H. Thwaites (11/125. 'Annals and Mag.
of Nat. Hist.' March 1848.) states that a seed from Fuchsia coccinea
fertilised by F. fulgens, contained two embryos, and was "a true vegetable
twin." The two plants produced from the two embryos were "extremely
different in appearance and character," though both resembled other hybrids
of the same parentage produced at the same time. These twin plants "were
closely coherent, below the two pairs of cotyledon-leaves, into a single
cylindrical stem, so that they had subsequently the appearance of being
branches on one trunk." Had the two united stems grown up to their full
height, instead of dying, a curiously mixed hybrid would have been
produced. A mongrel melon described by Sageret (11/126. 'Pomologie
Physiolog.' 1830 page 126.) may perhaps have thus originated; for the two
main branches, which arose from two cotyledon-buds, produced very different
fruit,--on the one branch like that of the paternal variety, and on the
other branch like to a certain extent that of the maternal variety, the
melon of China.]
In most of these cases of crossed varieties, and in some of the cases of
crossed species, the colours proper to both parents appeared in the
seedlings, as soon as they first flowered, in the form of stripes or larger
segments, or as whole flowers or fruit of different kinds borne on the same
plant; and in this case the appearance of the two colours cannot strictly
be said to be due to reversion, but to some incapacity of fusion. When,
however, the later flowers or fruit produced during the same season, or
during a succeeding year or generation, become striped or half-and-half,
etc., the segregation of the two colours is strictly a case of reversion by
bud-variation. Whether all the many recorded cases of striped flowers and
fruit are due to previous hybridisation and reversion is by no means clear,
for instance with peaches and nectarines, moss-roses, etc. In a future
chapter I shall show that, with animals of crossed parentage, the same
individual has been known to change its character during growth, and to
revert to one of its parents which it did not at first resemble. Finally,
from the various facts now given, there can be no doubt that the same
individual plant, whether a hybrid or a mongrel, sometimes returns in its
leaves, flowers, and fruit, either wholly or by segments, to both parent-
forms.
ON THE DIRECT OR IMMEDIATE ACTION OF THE MALE ELEMENT ON THE MOTHER FORM.
Another remarkable class of facts must be here considered, firstly, because
they have a high physiological importance, and secondly, because they have
been supposed to account for some cases of bud-variation. I refer to the
direct action of the male element, not in the ordinary way on the ovules,
but on certain parts of the female plant, or in case of animals on the
subsequent progeny of the female by a second male. I may premise that with
plants the ovarium and the coats of the ovules are obviously parts of the
female, and it could not have been anticipated that they would have been
affected by the pollen of a foreign variety or species, although the
development of the embryo, inside the embryonic sack, inside the ovule and
ovarium, of course, depends on the male element.
[Even as long ago as 1729 it was observed (11/127. 'Philosophical
Transact.' volume 43 1744-45 page 525.) that white and blue varieties of
the Pea, when planted near each other, mutually crossed, no doubt through
the agency of bees, and in the autumn blue and white peas were found within
the same pods. Wiegmann made an exactly similar observation in the present
century. The same result has followed several times when a variety with
peas of one colour has been artificially crossed by a differently-coloured
variety. (11/128. Mr. Goss 'Transact. Hort. Soc.' volume 5 page 234: and
Gartner 'Bastarderzeugung' 1849 ss. 81 and 499.) These statements led
Gartner, who was highly sceptical on the subject, carefully to try a long
series of experiments: he selected the most constant varieties, and the
result conclusively showed that the colour of the skin of the pea is
modified when pollen of a differently coloured variety is used. This
conclusion has since been confirmed by experiments made by the Rev. J.M.
Berkeley. (11/129. 'Gardener's Chronicle' 1854 page 404.)
Mr. Laxton of Stamford, whilst making experiments on peas for the express
purpose of ascertaining the influence of foreign pollen on the mother-
plant, has recently (11/130. Ibid 1866 page 900.) observed an important
additional fact. He fertilised the Tall Sugar-pea, which bears very thin
green pods, becoming brownish-white when dry, with pollen of the Purple-
podded pea, which, as its name expresses, has dark-purple pods with very
thick skin, becoming pale reddish purple when dry. Mr. Laxton has
cultivated the tall sugar-pea during twenty years, and has never seen or
heard of it producing a purple pod: nevertheless, a flower fertilised by
pollen from the purple-pod yielded a pod clouded with purplish-red which
Mr. Laxton kindly gave to me. A space of about two inches in length towards
the extremity of the pod, and a smaller space near the stalk, were thus
coloured. On comparing the colour with that of the purple pod, both pods
having been first dried and then soaked in water, it was found to be
identically the same; and in both the colour was confined to the cells
lying immediately beneath the outer skin of the pod. The valves of the
crossed pod were also decidedly thicker and stronger than those of the pods
of the mother-plant, but this may possibly have been an accidental
circumstance, for I know not how far their thickness is a variable
character in the Tall Sugar-pea.
The peas of the Tall Sugar-pea, when dry, are pale greenish-brown, thickly
covered with dots of dark purple so minute as to be visible only through a
lens, and Mr. Laxton has never seen or heard of this variety producing a
purple pea; but in the crossed pod one of the peas was of a uniform
beautiful violet-purple tint, and a second was irregularly clouded with
pale purple. The colour lies in the outer of the two coats which surround
the pea. As the peas of the purple-podded variety when dry are of a pale
greenish-buff, it would at first appear that this remarkable change of
colour in the peas in the crossed pod could not have been caused by the
direct action of the pollen of the purple-pod: but when we bear in mind
that this latter variety has purple flowers, purple marks on its stipules,
and purple pods; and that the Tall Sugar-pea likewise has purple flowers
and stipules, and microscopically minute purple dots on the peas, we can
hardly doubt that the tendency to the production of purple in both parents
has in combination modified the colour of the peas in the crossed pod.
After having examined these specimens, I crossed the same two varieties,
and the peas in one pod but not the pods themselves, were clouded and
tinted with purplish-red in a much more conspicuous manner than the peas in
the uncrossed pods produced at the same time by the same plants. I may
notice as a caution that Mr. Laxton sent me various other crossed peas
slightly, or even greatly, modified in colour; but the change in these
cases was due, as had been suspected by Mr. Laxton, to the altered colour
of the cotyledons, seen through the transparent coats of the peas; and as
the cotyledons are parts of the embryo, these cases are not in any way
remarkable.
Turning now to the genus Matthiola. The pollen of one kind of stock
sometimes affects the colour of the seeds of another kind, used as the
mother-plant. I give the following case the more readily, as Gartner
doubted similar statements previously made with respect to the stock by
other observers. A well-known horticulturist, Major Trevor Clarke, informs
me (11/131. See also a paper by this observer read before the International
Hort. and Bot. Congress of London 1866.) that the seeds of the large red-
flowered BIENNIAL stock, Matthiola annua (Cocardeau of the French), are
light brown, and those of the purple branching Queen stock (M. incana) are
violet-black; and he found that, when flowers of the red stock were
fertilised by pollen from the purple stock, they yielded about fifty per
cent of BLACK seeds. He sent me four pods from a red flowered plant, two of
which had been fertilised by their own pollen, and they included pale brown
seed; and two which had been crossed by pollen from the purple kind, and
they included seeds all deeply tinged with black. These latter seeds
yielded purple-flowered plants like their father; whilst the pale brown
seeds yielded normal red-flowered plants; and Major Clarke, by sowing
similar seeds, has observed on a greater scale the same result. The
evidence in this case of the direct action of the pollen of one species on
the colour of the seeds of another species appears to me conclusive.
Gallesio (11/132. 'Traite du Citrus' page 40.) fertilised the flowers of an
orange with pollen from the lemon; and one fruit thus produced bore a
longitudinal stripe of peel having the colour, flavour, and other
characters of the lemon. Mr. Anderson (11/133. 'Transact. Hort. Soc.'
volume 3 page 318. See also volume 5 page 65.) fertilised a green-fleshed
melon with pollen from a scarlet-fleshed kind; in two of the fruits "a
sensible change was perceptible: and four other fruits were somewhat
altered both internally and externally." The seeds of the two first-
mentioned fruits produced plants partaking of the good properties of both
parents. In the United States, where Cucurbitaceae are largely cultivated,
it is the popular belief (11/134. Prof. Asa Gray 'Proc. Acad. Sc.' Boston
volume 4 1860 page 21. I have received statements to the same effect from
other persons in the United States.) that the fruit is thus directly
affected hy foreign pollen; and I have received a similar statement with
respect to the cucumber in England. It is believed that grapes have been
thus affected in colour, size, and shape: in France a pale-coloured grape
had its juice tinted by the pollen of the dark-coloured Teinturier; in
Germany a variety bore berries which were affected by the pollen of two
adjoining kinds; some of the berries being only partially affected or
mottled. (11/135. For the French case see 'Journ. Hort. Soc.' volume 1 new
series 1866 page 50. For Germany see M. Jack quoted in Henfrey's 'Botanical
Gazette' volume 1 page 277. A case in England has recently been alluded to
by the Rev. J.M. Berkeley before the Hort. Soc. of London.)
As long ago as 1751 (11/136. 'Philosophical Transactions' volume 47 1751-52
page 206.) it was observed that, when differently-coloured varieties of
maize grew near each other, they mutually affected each other's seeds, and
this is now a popular belief in the United States. Dr. Savi (11/137.
Gallesio 'Teoria della Riproduzione' 1816 page 95.) tried the experiment
with care: he sowed yellow and black-seeded maize together, and on the same
ear some of the seeds were yellow, some black, and some mottled, the
differently coloured seeds being arranged irregularly or in rows. Prof.
Hildebrand has repeated the experiment (11/138. 'Bot. Zeitung' May 1868
page 326.) with the precaution of ascertaining that the mother-plant was
true. A kind bearing yellow grains was fertilised with pollen of a kind
having brown grains, and two ears produced yellow grains mingled with
others of a dirty violet tint. A third ear had only yellow grains, but one
side of the spindle was tinted of a reddish-brown; so that here we have the
important fact of the influence of the foreign pollen extending to the
axis. Mr. Arnold, in Canada, varied the experiment in an interesting
manner: "a female flower was subjected first to the action of pollen from a
yellow variety, and then to that from a white variety; the result was an
ear, each grain of which was yellow below and white above." (11/139. See
Dr. J. Stockton-Hough 'American Naturalist' January 1874 page 29.) With
other plants it has occasionally been observed that the crossed offspring
showed the influence of two kinds of pollen, but in this case the two kinds
affected the mother-plant.
Mr. Sabine states (11/140. 'Transact. Hort. Soc.' volume 5 page 69.) that
he has seen the form of the nearly globular seed-capsule of Amaryllis
vittata altered by the application of the pollen of another species, of
which the capsule has gibbous angles. With an allied genus, a well-known
botanist, Maximowicz, has described in detail the striking results of
reciprocally fertilising Lilium bulbiferum and davuricum with each other's
pollen. Each species produced fruit not like its own, but almost identical
with that of the pollen-bearing species; but from an accident only the
fruit of the latter species was carefully examined; the seeds were
intermediate in the development of their wings. (11/141. 'Bull. de l'Acad.
Imp. de St. Petersburg' tome 17 page 275, 1872. The author gives references
to those cases in the So1anaceae of fruit affected by foreign pollen, but
as it does not appear that the mother-plant was artificially fertilised, I
have not entered into details.)
Fritz Muller fertilised Cattleya leopoldi with pollen of Epidendron
cinnabarinum; and the capsules contained very few seeds; but these
presented a most wonderful appearance, which, from the description given,
two botanists, Hildebrand and Maximowicz, attribute to the direct action of
the pollen of the Epidendron. (11/142. 'Bot. Zeitung' September 1868 page
631. For Maximowicz's judgment see the paper last referred to.)
Mr. J. Anderson Henry (11/143. 'Journal of Horticulture' January 20, 1863
page 46.) crossed Rhododendron dalhousiae with the pollen of R. nuttallii,
which is one of the largest-flowered and noblest species of the genus. The
largest pod produced by the former species, when fertilised with its own
pollen, measured 1 2/8 inch in length and 1 1/2 in girth; whilst three of
the pods which had been fertilised by pollen of R. nuttallii measured 1 5/8
inch in length and no less than 2 inches in girth. Here the effect of the
foreign pollen was apparently confined to increasing the size of the
ovarium; but we must be cautious in assuming, as the following case shows,
that size had been transferred from the male parent to the capsule of the
female plant. Mr. Henry fertilised Arabis blepharophylla with pollen of A.
soyeri, and the pods thus produced, of which he was so kind as to send me
detailed measurements and sketches, were much larger in all their
dimensions than those naturally produced by either the male or female
parent-species. In a future chapter we shall see that the organs of
vegetation in hybrid plants, independently of the character of either
parent, are sometimes developed to a monstrous size; and the increased size
of the pods in the foregoing cases may be an analogous fact. On the other
hand, M. de Saporta informs me that an isolated female plant of Pistacia
vera is very apt to be fertilised by the pollen of neighbouring plants of
P. terebinthus, and in this case the fruits are only half their proper
size, which he attributes to the influence of the pollen of P. terebinthus.
No case of the direct action of the pollen of one variety on another is
better authenticated or more remarkable than that of the common apple. The
fruit here consists of the lower part of the calyx and of the upper part of
the flower-peduncle (11/144. See on this head the high authority of Prof.
Decaisne in a paper translated in 'Journ. Hort. Soc.' volume 1 new series
1866 page 48.) in a metamorphosed condition, so that the effect of the
foreign pollen has extended even beyond the limits of the ovarium. Cases of
apples thus affected were recorded by Bradley in the early part of the last
century; and other cases are given in old volumes of the 'Philosophical
Transactions' (11/145. Volume 43 1744-45 page 525 volume 45 1747-48 page
602.); in one of these a Russeting apple and an adjoining kind mutually
affected each other's fruit; and in another case a smooth apple affected a
rough-coated kind. Another instance has been given (11/146. 'Transact.
Hort. Soc.' volume 5 pages 65 and 68. See also Prof. Hildebrand with a
coloured figure in 'Bot. Zeitung' May 15, 1868 page 327. Puvis also has
collected 'De La Degeneration' 1837 page 36) several other instances; but
it is not in all cases possible to distinguish between the direct action of
foreign pollen and bud-variations.) of two very different apple-trees
growing close to each other, which bore fruit resembling each other, but
only on the adjoining branches. It is, however, almost superfluous to
adduce these or other cases, after that of the St. Valery apple, the
flowers which, from the abortion of the stamens, do not produce pollen, but
are fertilised by the girls of the neighbourhood with pollen of many kinds;
and they bear fruit, "differing from one another in size, flavour, and
colour, but resembling in character the hermaphrodite kinds by which they
have been fertilised." (11/147. T. de Clermont-Tonnerre in 'Mem. de la Soc.
Linn. de Paris' tome 3 1825 page 164.)]
I have now shown, on the authority of several excellent observers, in the
case of plants belonging to widely different orders, that the pollen of one
species or variety, when applied to the female of a distinct form,
occasionally causes the coats of the seeds, the ovarium or fruit, including
even the calyx and upper part of the peduncle of the apple, and the axis of
the ear in maize, to be modified. Sometimes the whole ovarium or all the
seeds are thus affected; sometimes only a certain number of the seeds, as
in the case of the pea, or only a part of the ovarium, as with the striped
orange, mottled grapes, and maize, is thus affected. It must not be
supposed that any direct or immediate effect invariably follows the use of
foreign pollen: this is far from being the case; nor is it known on what
conditions the result depends. Mr. Knight (11/148. 'Transact. of Hort.
Soc.' volume 5 page 68.) expressly states that he has never seen the fruit
thus affected, though he crossed thousands of apple and other fruit-trees.
There is not the least reason to believe that a branch which has borne seed
or fruit directly modified by foreign pollen is itself affected, so as
afterwards to produce modified buds; such an occurrence, from the temporary
connection of the flower with the stem, would be hardly possible. Hence,
but very few, if any, of the cases of bud-variation in the fruit of trees,
given in the early part of this chapter can be accounted for by the action
of foreign pollen; for such fruits have commonly been propagated by budding
or grafting. It is also obvious that changes of colour in flowers, which
necessarily supervene long before they are ready for fertilisation, and
changes in the shape or colour of leaves, when due to the appearance of
modified buds, can have no relation to the action of foreign pollen.
The proofs of the action of foreign pollen on the mother-plant have been
given in considerable detail, because this action, as we shall see in a
future chapter, is of the highest theoretical importance, and because it is
in itself a remarkable and apparently anomalous circumstance. That it is
remarkable under a physiological point of view is clear, for the male
element not only affects, in accordance with its proper function, the germ,
but at the same time various parts of the mother-plant, in the same manner,
as it affects the same part in the seminal offspring from the same two
parents. We thus learn that an ovule is not indispensable for the reception
of the influence of the male element. But this direct action of the male
element is not so anomalous as it at first appears, for it comes into play
in the ordinary fertilisation of many flowers. Gartner gradually increased
the number of pollen grains until he succeeded in fertilising a Malva, and
has (11/149. Beitrage zur Kenntniss der Befruchtung' 1844 s. 347-351.)
proved that many grains are first expended in the development, or, as he
expresses it, in the satiation, of the pistil and ovarium. Again, when one
plant is fertilised by a widely distinct species, it often happens that the
ovarium is fully and quickly developed without any seeds being formed; or
the coats of the seeds are formed without any embryo being developed
within. Prof. Hildebrand, also, has lately shown (11/150. 'Die
Fruchtbildung der Orchideen, ein Beweis fur die doppelte Wirkung des
Pollens' 'Botanische Zeitung' No. 44 et seq. October 30, 1865; and August
4, 1865 s. 249.) that, in the normal fertilisation of several Orchideae,
the action of the plant's own pollen is necessary for the development of
the ovarium; and that this development takes place not only long before the
pollen-tubes have reached the ovules, but even before the placentae and
ovules have been formed; so that with these orchids the pollen acts
directly on the ovarium. On the other hand, we must not overrate the
efficacy of pollen in the case of hybridised plants, for an embryo may be
formed and its influence excite the surrounding tissues of the mother-
plant, and then perish at a very early age and be thus overlooked. Again,
it is well known that with many plants the ovarium may be fully developed,
though pollen be wholly excluded. Lastly, Mr. Smith, the late Curator at
Kew (as I hear through Dr. Hooker), observed with an orchid, the Bonatea
speciosa, the singular fact that the development of the ovarium could be
effected by the mechanical irritation of the stigma. Nevertheless, from the
number of the pollen-grains expended "in the satiation of the ovarium and
pistil,"--from the generality of the formation of the ovarium and seed-
coats in hybridised plants which produce no seeds,--and from Dr.
Hildebrand's observations on orchids, we may admit that in most cases the
swelling of the ovarium, and the formation of the seed-coats are at least
aided, if not wholly caused, by the direct action of the pollen,
independently of the intervention of the fertilised germ. Therefore, in the
previously given cases we have only to believe in the further power of
pollen, when applied to a distinct species or variety, to influence the
shape, size, colour, texture, etc., of certain parts of the mother-plant.
Turning now to the animal kingdom. If we could imagine the same flower to
yield seeds during successive years, then it would not be very surprising
that a flower of which the ovarium had been modified by foreign pollen
should next year produce, when self-fertilised, offspring modified by the
previous male influence. Closely analogous cases have actually occurred
with animals. In the case often quoted from Lord Morton (11/151. 'Philos.
Transact.' 1821 page 20.) a nearly purely-bred Arabian chestnut mare bore a
hybrid to a quagga; she was subsequently sent to Sir Gore Ouseley, and
produced two colts by a black Arabian horse. These colts were partially
dun-coloured, and were striped on the legs more plainly than the real
hybrid, or even than the quagga. One of the two colts had its neck and some
other parts of its body plainly marked with stripes. Stripes on the body,
not to mention those on the legs, are extremely rare,--I speak after having
long attended to the subject,--with horses of all kinds in Europe, and are
almost unknown in the case of Arabians. But what makes the case still more
striking is that in these colts the hair of the mane resembled that of the
quagga, being short, stiff, and upright. Hence there can be no doubt that
the quagga affected the character of the offspring subsequently begot by
the black Arabian horse. Mr. Jenner Weir informs me of a strictly parallel
case: his neighbour Mr. Lethbridge, of Blackheath, has a horse, bred by
Lord Mostyn, which had previously borne a foal by a quagga. This horse is
dun with a dark stripe down the back, faint stripes on the forehead between
the eyes, plain stripes on the inner side of the fore-legs and rather more
faint ones on the hind-legs, with no shoulder-stripe. The mane grows much
lower on the forehead than in the horse, but not so low as in the quagga or
zebra. The hoofs are proportionally longer than in the horse,--so much so
that the farrier who first shod this animal, and knew nothing of its
origin, said, "Had I not seen I was shoeing a horse, I should have thought
I was shoeing a donkey."
With respect to the varieties of our domesticated animals, many similar and
well-authenticated facts have been published (11/152. Dr. Alex. Harvey on
'A remarkable Effect of Cross-breeding' 1851. On the 'Physiology of
Breeding' by Mr. Reginald Orton 1855. 'Intermarriage' by Alex. Walker 1837.
'L'Heredite Naturelle' by Dr. Prosper Lucas tome 2 page 58. Mr. W. Sedgwick
in 'British and Foreign Medico-Chirurgical Review' 1863 July page 183.
Bronn in his 'Geschichte der Natur' 1843 b. 2 s. 127 has collected several
cases with respect to mares, sows, and dogs. Mr. W.C.L. Martin ('History of
the Dog' 1845 page 104) says he can personally vouch for the influence of
the male parent on subsequent litters by other dogs. A French poet, Jacques
Savary, who wrote in 1665 on dogs, was aware of this singular fact. Dr.
Bowerbank has given us the following striking case:--A black, hairless
Barbary bitch was first accidentally impregnated by a mongrel spaniel with
long brown hair, and she produced five puppies, three of which were
hairless and two covered with SHORT brown hair. The next time she was put
to a black, hairless Barbary dog; "but the mischief had been implanted in
the mother, and again about half the litter looked like pure Barbarys, and
the other half like the SHORT-haired progeny of the first father." I have
given in the text one case with pigs; an equally striking one has been
recently published in Germany, 'Illust. Landwirth. Zeitung' 1868 November
17 page 143. It is worth notice that farmers in S. Brazil (as I hear from
Fritz Muller), and at the C. of Good Hope (as I have heard from two
trustworthy persons) are convinced that mares which have once borne mules,
when subsequently put to horses, are extremely liable to produce colts,
striped like a mule. Dr. Wilckens of Pogarth gives ('Jahrbuch
Landwirthschaft' 2 1869 page 325) a striking and analogous case. A merino
ram, having two small lappets or flaps of skin on the neck, was in the
winter of 1861-62 put to several Merino ewes, all of whom bore lambs with
similar flaps on their necks. The ram was killed in the spring of 1862 and
subsequently to his death the ewes were put to other Merino rams, and in
1863 to Southdown rams, none of whom ever have neck lappets: nevertheless,
even as long afterwards as 1867, several of these ewes produced lambs
bearing these appendages.), and others have been communicated to me,
plainly showing the influence of the first male on the progeny subsequently
borne by the mother to other males. It will suffice to give a single
instance, recorded in the 'Philosophical Transactions,' in a paper
following that by Lord Morton: Mr. Giles put a sow of Lord Western's black
and white Essex breed to a wild boar of a deep chestnut colour; and the
"pigs produced partook in appearance of both boar and sow, but in some the
chestnut colour of the boar strongly prevailed." After the boar had long
been dead, the sow was put to a boar of her own black and white breed--a
kind which is well known to breed very true and never to show any chestnut
colour,--yet from this union the sow produced some young pigs which were
plainly marked with the same chestnut tint as in the first litter. Similar
cases have so frequently occurred, that careful breeders avoid putting a
choice female of any animal to an inferior male, on account of the injury
to her subsequent progeny which may be expected to follow.
Some physiologists have attempted to account for these remarkable results
from a previous impregnation, by the imagination of the mother having been
strongly affected; but it will hereafter be seen that there are very slight
grounds for any such belief. Other physiologists attribute the result to
the close attachment and freely intercommunicating blood-vessels between
the modified embryo and mother. But the analogy from the action of foreign
pollen on the ovarium, seed-coats, and other parts of the mother-plant,
strongly supports the belief that with animals the male element acts
directly on the female, and not through the crossed embryo. With birds
there is no close connection between the embryo and mother; yet a careful
observer, Dr. Chapuis, states (11/153. 'Le Pigeon Voyageur Belge' 1865 page
59.) that with pigeons the influence of a first male sometimes makes itself
perceived in the succeeding broods; but this statement requires
confirmation.
CONCLUSION AND SUMMARY OF THE CHAPTER.
The facts given in the latter half of this chapter are well worthy of
consideration, as they show us in how many extraordinary modes the union of
one form with another may lead to the modification of the seminal offspring
or of the buds, afterwards produced.
There is nothing surprising in the offspring of species or varieties
crossed in the ordinary manner being modified; but the case of two plants
within the same seed, which cohere and differ from each other, is curious.
When a bud is formed after the cellular tissue of two species or two
varieties have been united, and it partakes of the characters of both
parents, the case is wonderful. But I need not here repeat what has been so
lately said on this subject. We have also seen that in the case of plants
the male element may affect in a direct manner the tissues of the mother,
and with animals may lead to the modification of her future progeny. In the
vegetable kingdom the offspring from a cross between two species or
varieties, whether effected by seminal generation or by grafting, often
revert, to a greater or less degree, in the first or in a succeeding
generation, to the two parent-forms; and this reversion may affect the
whole flower, fruit, or leaf-bud, or only the half or a smaller segment of
a single organ. In some cases, however, such segregation of character
apparently depends on an incapacity for union rather than on reversion, for
the flowers or fruit which are first produced display by segments the
characters of both parents. The various facts here given ought to be well
considered by any one who wishes to embrace under a single point of view
the many modes of reproduction by gemmation, division, and sexual union,
the reparation of lost parts, variation, inheritance, reversion, and other
such phenomena. Towards the close of the second volume I shall attempt to
connect these facts together by the hypothesis of pangenesis.
In the early half of the present chapter I have given a long list of plants
in which through bud-variation, that is, independently of reproduction by
seed, the fruit has suddenly become modified in size, colour, flavour,
hairiness, shape, and time of maturity; flowers have similarly changed in
shape, colour, in being double, and greatly in the character of the calyx;
young branches or shoots have changed in colour, in bearing spines and in
habit of growth, as in climbing or in weeping; leaves have changed in
becoming variegated, in shape, period of unfolding, and in their
arrangement on the axis. Buds of all kinds, whether produced on ordinary
branches or on subterranean stems, whether simple or much modified and
supplied with a stock of nutriment, as in tubers and bulbs, are all liable
to sudden variations of the same general nature.
In the list, many of the cases are certainly due to reversion to characters
not acquired from a cross, but which were formerly present and have since
been lost for a longer or shorter time;--as when a bud on a variegated
plant produces plain leaves, or when the variously-coloured flowers of the
Chrysanthemum revert to the aboriginal yellow tint. Many other cases
included in the list are probably due to the plants being of crossed
parentage, and to the buds reverting either completely or by segments to
one of the two parent-forms. (11/154. It may be worth while to call
attention to the several means by which flowers and fruit become striped or
mottled. Firstly, by the direct action of the pollen of another variety or
species, as in the cases given of oranges and maize. Secondly, in crosses
of the first generation, when the colours of the two parents do not readily
unite, as with Mirabilis and Dianthus. Thirdly, in crossed plants of a
subsequent generation by reversion, through either bud or seminal
generation. Fourthly, by reversion to a character not originally gained by
a cross, but which had long been lost, as with white-flowered varieties,
which we shall hereafter see often become striped with some other colour.
Lastly, there are cases, as when peaches are produced with a half or
quarter of the fruit like a nectarine, in which the change is apparently
due to mere variation, through either bud or seminal generation.)
We may suspect that the strong tendency in the Chrysanthemum to produce by
bud-variation differently-coloured flowers, results from the varieties
having been at some time intentionally or accidentally crossed; and this is
certainly the case with some kinds of Pelargonium. So it may be to a large
extent with the bud-varieties of the Dahlia, and with the "broken colours
"of Tulips. When, however, a plant reverts by bud-variation to its two
parent forms, or to one of them, it sometimes does not revert perfectly,
but assumes a somewhat new character,--of which fact, instances have been
given, and Carriere gives (11/155. 'Production des Varietes' page 37.)
another in the cherry.
Many cases of bud-variation, however, cannot be attributed to reversion,
but to so-called spontaneous variability, as is so common with cultivated
plants raised from seed. As a single variety of the Chrysanthemum has
produced by buds six other varieties, and as one variety of the gooseberry
has borne at the same time four distinct kinds of fruit, it is scarcely
possible to believe that all these variations are due to reversion. We can
hardly believe, as remarked in a previous chapter, that all the many
peaches which have yielded nectarine-buds are of crossed parentage. Lastly,
in such cases as that of the moss-rose, with its peculiar calyx, and of the
rose which bears opposite leaves, in that of the Imatophyllum, etc., there
is no known natural species or variety from which the characters in
question could have been derived by a cross. We must attribute all such
cases to the appearance of absolutely new characters in the buds. The
varieties which have thus arisen cannot be distinguished by any external
character from seedlings; this is notoriously the case with the varieties
of the Rose, Azalea, and many other plants. It deserves notice that all the
plants which have yielded bud-variations have likewise varied greatly by
seed.
The plants which have varied by buds belong to so many orders that we may
infer that almost every plant would be liable to variation, if placed under
the proper exciting conditions. These conditions, as far as we can judge,
mainly depend on long-continued and high cultivation; for almost all the
plants in the foregoing list are perennials, and have been largely
propagated in many soils, under different climates, by cuttings, offsets,
bulbs, tubers, and especially by budding or grafting. The instances of
annuals varying by buds, or producing on the same plant differently
coloured flowers, are comparatively rare: Hopkirk (11/156. 'Flora Anomala'
page 164.) has seen this with Convolvulus tricolor; and it is not uncommon
with the Balsam and annual Delphinium. According to Sir R. Schomburgk,
plants from the warmer temperate regions, when cultivated under the hot
climate of St. Domingo, are eminently liable to bud-variation. I am
informed by Mr. Sedgwick that moss-roses which have often been taken to
Calcutta always there lose their mossiness; but change of climate is by no
means a necessary contingent, as we see with the gooseberry, currant, and
in many other cases. Plants living under their natural conditions are very
rarely subject to bud-variation. Variegated leaves have, however, been
observed under such circumstances; and I have given an instance of
variation by buds on an ash-tree planted in ornamental grounds, but it is
doubtful whether such a tree can be considered as living under strictly
natural conditions. Gartner has seen white and dark-red flowers produced
from the same root of the wild Achillea millefolium; and Prof. Caspary has
seen a completely wild Viola lutea bearing flowers of two different colours
and sizes. (11/157. 'Schriften der physisch-okon. Gesell. zu Konigsberg' b.
6 February 3, 1865 s. 4.)
As wild plants are so rarely liable to bud-variation, whilst highly
cultivated plants long propagated by artificial means have yielded many
varieties by this form of reproduction, we are led through a series such as
the following,--namely, all the eyes in the same tuber of the potato
varying in the same manner,--all the fruit on a purple plum-tree suddenly
becoming yellow,--all the fruit on a double-flowered almond suddenly
becoming peach like,--all the buds on grafted trees being in a very slight
degree affected by the stock on which they have been worked,--all the
flowers on a transplanted heartsease changing for a time in colour, size,
and shape,--we are led by such a series to look at every case of bud-
variation as the direct result of the conditions of life to which the plant
has been exposed. On the other hand, plants of the same variety may be
cultivated in two adjoining beds, apparently under exactly the same
conditions, and those in the one bed, as Carriere insists (11/158.
'Production des Varietes' pages 58, 70.) will produce many bud-variations,
and those in the other not a single one. Again, if we look to such cases as
that of a peach-tree which, after having been cultivated by tens of
thousands during many years in many countries, and after having annually
produced millions of buds, all of which have apparently been exposed to
precisely the same conditions, yet at last suddenly produces a single bud
with its whole character greatly transformed, we are driven to the
conclusion that the transformation stands in no DIRECT relation to the
conditions of life.
We have seen that varieties produced from seeds and from buds resemble each
other so closely in general appearance that they cannot be distinguished.
Just as certain species and groups of species, when propagated by seed, are
more variable than other species or genera, so it is in the case of certain
bud-varieties. Thus, the Queen of England Chrysanthemum has produced by
this latter process no less than six, and Rollisson's Unique Pelargonium
four distinct varieties; moss-roses have also produced several other moss-
roses. The Rosaceae have varied by buds more than any other group of
plants; but this may be in large part due to so many members having been
long cultivated; but within this same group, the peach has often varied by
buds, whilst the apple and pear, both grafted trees extensively cultivated,
have afforded, as far as I can ascertain, extremely few instances of bud-
variation.
The law of analogous variation holds good with varieties produced by buds,
as with those produced from seed: more than one kind of rose has sported
into a moss-rose; more than one kind of camellia has assumed an hexagonal
form; and at least seven or eight varieties of the peach have produced
nectarines.
The laws of inheritance seem to be nearly the same with seminal and bud-
varieties. We know how commonly reversion comes into play with both, and it
may affect the whole, or only segments of a leaf, flower, or fruit. When
the tendency to reversion affects many buds on the same tree, it becomes
covered with different kinds of leaves, flowers, or fruit; but there is
reason to believe that such fluctuating varieties have generally arisen
from seed. It is well known that, out of a number of seedling varieties,
some transmit their character much more truly by seed than others; so with
bud-varieties, some retain their character by successive buds more truly
than others; of which instances have been given with two kinds of
variegated Euonymus and with certain kinds of tulips and pelargoniums.
Notwithstanding the sudden production of bud-varieties, the characters thus
acquired are sometimes capable of transmission by seminal reproduction: Mr.
Rivers has found that moss-roses generally reproduce themselves by seed;
and the mossy character has been transferred by crossing from one species
of rose to another. The Boston nectarine, which appeared as a bud-
variation, produced by seed a closely allied nectarine. On the other hand,
seedlings from some bud-variations have proved variable to an extreme
degree. (11/159. Carriere 'Production des Varietes' page 39.) We have also
heard, on the authority of Mr. Salter, that seeds taken from a branch with
leaves variegated through bud-variation, transmit this character very
feebly; whilst many plants, which were variegated as seedlings, transmit
variegation to a large proportion of their progeny.
Although I have been able to collect a good many cases of bud-variation, as
shown in the previous lists, and might probably, by searching foreign
horticultural works, have collected very many more cases, yet their total
number is as nothing in comparison with that of seminal varieties. With
seedlings raised from the more variable cultivated plants, the variations
are almost infinitely numerous, but their differences are generally slight:
only at long intervals of time a strongly marked modification appears. On
the other hand, it is a singular and inexplicable fact that, when plants
vary by buds, the variations, though they occur with comparative rarity,
are often, or even generally, strongly pronounced. It struck me that this
might perhaps be a delusion, and that slight changes often occurred in
buds, but were overlooked or not recorded from being of no value.
Accordingly, I applied to two great authorities on this subject, namely, to
Mr. Rivers with respect to fruit-trees, and to Mr. Salter with respect to
flowers. Mr. Rivers is doubtful, but does not remember having noticed very
slight variations in fruit-buds. Mr. Salter informs me that with flowers
such do occur, but, if propagated, they generally lose their new character
in the following year; yet he concurs with me that bud-variations usually
at once assume a decided and permanent character. We can hardly doubt that
this is the rule, when we reflect on such cases as that of the peach, which
has been so carefully observed, and of which such trifling seminal
varieties have been propagated, yet this tree has repeatedly produced by
bud-variation nectarines, and only twice (as far as I can learn) any other
variety, namely, the Early and Late Grosse Mignonne peaches; and these
differ from the parent-tree in hardly any character except the period of
maturity.
To my surprise, I hear from Mr. Salter that he brings the principle of
selection to bear on variegated plants propagated by buds, and has thus
greatly improved and fixed several varieties. He informs me that at first a
branch often produces variegated leaves on one side alone, and that the
leaves are marked only with an irregular edging or with a few lines of
white and yellow. To improve and fix such varieties, he finds it necessary
to encourage the buds at the bases of the most distinctly marked leaves,
and to propagate from them alone. By following with perseverance this plan
during three or four successive seasons, a distinct and fixed variety can
generally be secured.
Finally, the facts given in this chapter prove in how close and remarkable
a manner the germ of a fertilised seed and the small cellular mass forming
a bud, resemble each other in all their functions--in their power of
inheritance with occasional reversion,--and in their capacity for variation
of the same general nature, in obedience to the same laws. This
resemblance, or rather identity of character, is shown in the most striking
manner by the fact that the cellular tissue of one species or variety, when
budded or grafted on another, may give rise to a bud having an intermediate
character. We have seen that variability does not depend on sexual
generation, though much more frequently its concomitant than of bud
reproduction. We have seen that bud-variability is not solely dependent on
reversion or atavism to long-lost characters, or to those formerly acquired
from a cross, but appears often to be spontaneous. But when we ask
ourselves what is the cause of any particular bud-variation, we are lost in
doubt, being driven in some cases to look to the direct action of the
external conditions of life as sufficient, and in other cases to feel a
profound conviction that these have played a quite subordinate part, of not
more importance than the nature of the spark which ignites a mass of
combustible matter.