PAGE
I Rustic Sounds 1
II Francis Galton 13
III The Movement of Plants 36
IV A Lane in the Cotswolds 55
V Jane Austen 61
VI The Education of a Man of Science 78
VII The Pipe and Tabor 97
VIII Stephen Hales 115
IX Nullius in Verba 140
X Sir George Darwin 152
XI War Music 195
XII The Teaching of Science 201
XIII Picturesque Experiments 210
XIV Dogs and Dog Lovers 219
Plate Pipe and Tabor to face 102
To
F. H. D.
I
RUSTIC SOUNDS
Sounds are to me more reminiscent than sights; they bring back the
sensations of childhood, and indeed all memories of my past life, in a
way more touching and clear than what is seen. Wendell Holmes claims the
sense of smell as most closely associated with memory; for me, as I say,
it is that of hearing.
In this paper I shall wander in imagination through the different seasons
in the home of my youth, and let the recalled rustic sounds lead where
they will.
To children there is something impressive and almost sacred in the
changes of the seasons, in the onset of winter, or the clear approach of
spring. The first of these changes was heralded for me by the appearance
of puddles frozen to a shining white; mysterious because the frost had
drunk them dry in roofing them with ice, and especially delightful in the
sharp crackling sound they gave when trodden on. This was the noise of
the beginning of winter. Another winter memory is the humming whistle of
the boys' feet as they slid on the village pond, a remembrance that
recalls my envious admiration of their heavily nailed boots, giving them
an advantage in pace and a more noble style of sliding.
Another familiar sound was the wicked groaning crack that ran round the
solitary pond on which we skated, as it unwillingly settled down to bear
us on its surface. It had a threat in it, and reminded us how helpless
we were, that the pond-spirit was our master and had our lives in its
grip.
Another winter note was the hooting of invisible owls, boldly calling to
each other from one moonlit tree to another. In the spring there was the
querulous sound of the lambs, staggering half fledged in the cold fields
among the half-eaten turnips beside their dirty yellow mothers. Not the
sheep of the Dresden shepherdess, but rather of the old man in _As You
Like It_, who warns Rosalind that shepherding has its ugly side. Yet it
had something prophetic of more genial days.
[Picture: Whistle: Fig. 1] As the sap began to rise in the trees my
thoughts lightly turned to the making of whistles. I was taught the
mystery by a labourer in my father's employ and never departed from his
method. The first thing was to cut a branch of some likely tree, a
horse-chestnut for choice, severing it by an oblique cut, removing a ring
of bark R and notching it at N. The bark had then to be removed in one
piece so as to make the tube of the whistle. The first thing was to suck
the bark and thoroughly wet it--a process I now believe to have been
entirely useless. The bark was next hammered all over with the haft of
the knife, which was held by the blade. Then when the inner layer of the
bark was well bruised, it could be removed in one piece. To effect this
I was taught to hold it in my handkerchief, and after a twist or two, a
delicious yielding was experienced and the bark slipped off. The shiny
white stick which remained in the other hand had to be cut in half,
shaved in a particular way and again fitted into its bark tube. Then
came the exciting moment,--would the thing whistle? The joy was short
lived, and the whistles soon dried and shrank and ceased to satisfy the
artist. But it was always possible to make a new one.
Since the above description was written, there has appeared in _The
Times_ Literary Supplement (February 22, 1917, p. 90) a notice of the
poems of a Canadian writer {3} from which the reviewer quotes the
following beautiful lines:
"So in the shadow by the nimble flood,
He made her whistles of the willow wood,
Flutes of one note with mellow slender tone;
(A robin piping in the dark alone).
Lively the pleasure was the wand to bruise,
And notch the light rod for its lyric use,
Until the stem gave up its slender sheath,
And showed the white and glistening wood beneath.
And when the ground was covered with light chips,
Grey leaves and green, and twigs and tender slips," . . .
This could only have been written by one perfectly familiar with the art
of whistle-making. But it seems to have been misunderstood by the
reviewer, who says that he "once came upon one of these small AEolian
harps in a wooded isle in the 'Land of Afternoon,'" . . . and decided
"that it was a work of superstition by Indian hands." As an AEolian harp
is a stringed instrument sounded by the wind, and a whistle belongs to
the very distinct class of musical things sounded by human breath, I can
only suppose that the reviewer has misunderstood the poem.
I cannot leave the Canadian poet without a reference to the beautiful
line, ("A robin piping in the dark alone.") A Canadian robin must surely
make a song like ours, who seems also to sing in parenthesis.
The other form of rustic pipe that pleased me was a sort of oboe made
from a dandelion stalk by squeezing it at one end. It had a rough nasal
note, which could be controlled by holes cut in the stalk and stopped
with the fingers. This again was but brief satisfaction, for the two
halves of the reed soon curled outwards and ceased to speak. In later
life this curling outwards was made use of in my work in the physiology
of plants. I like to remember that my primeval oboe gave me the idea.
The village boys made 'musics' by fixing strips of laurel leaf into a
split stick, and blowing violently into them, which set the leaf
vibrating and made a coarse scream, but this instrument we despised, and
I think rightly, for it had none of the pleasant tone of the whistle, nor
was there any art in the making of it.
A primeval musical instrument called the 'Whit horn' I have seen in the
possession of the late Mr. Taphouse, of Oxford. It is a conical tube of
bark held together with thorns and sounded by means of a rough oboe-reed
made of bark; there were no finger-holes, and is said to have yielded a
harsh shriek on one note. It was, I think, played on May 1st, or else at
Whitsuntide. It is to Mr. Taphouse that I owe my introduction to the
pipe and tabor which form the subject of a paper in this volume. The
pipe is shrill in its upper register, but this is no great fault in an
instrument meant to be played out of doors: the same fault is to be found
with the flageolet, and the penny whistle. But the last named instrument
is reminiscent of a man playing outside a London public-house, and we
know from the story of the perfidious Sergeant in _The Wrong Box_ to what
lengths it may lead us. {5}
The most truly rustic instrument (and here I mean an instrument of polite
life--an orchestral instrument) is undoubtedly the oboe. The bassoon
runs it hard, but has a touch of comedy and a stronger flavour of
necromancy, while the oboe is quite good and simple in nature and is
excessively in earnest; it seems to have in it the ghost of a sunburnt
boy playing to himself under a tree, in a ragged shirt unbuttoned at the
throat, a boy created by Velasquez. To hear an oboe actually played as a
rustic instrument one must go to Brittany, where it accompanies the
national bagpipe or 'biniou.' To a reed-instrument player it was painful
to see the oboist bite a bit off his reed when the tone was not to his
liking!
From this digression, originating in the whistle cut from a
horse-chestnut bough, I return to some less artificial sounds. I must
say a word about the song of birds, but my knowledge of the subject is
but small. The most obvious of spring-time sounds is the voice of the
cuckoo. I confess to liking the muttering chuckle which, in an
unscientific mood, I have supposed to mean that an egg has successfully
been laid in a hedge-sparrow's nest. But the cuckoo's "word in a minor
third" is always delightful. The bird is neither more nor less of a
foreigner than a willow-wren, yet he has, in comparison to the wren's
subdued chromatic warble, a song so self-assertive, and a tone so unlike
our other birds, that one feels him an obvious exotic, a foreigner of so
glorious and dashing a nature that one is grateful to him for singing
among flat ploughed lands and monotonous hedges. I fancy the Welsh
proverb, "Who would have thought the cuckoo would sing on the turf-heaps
of the mountains," is a poetic reflexion of this thought.
Of the nightingale I have nothing to say, except to put on record a true
remark of Sir Charles Stanford's, viz., that he sings in a syncopated
rhythm. But, though I lived in a nightingale land, it is another bird
that most clearly brings back to me the country of my boyhood, I mean the
night-jar. He has something of antique mystery which I do not find in
the nightingale, as he purrs on his only note through the warm night.
There is something unknown and primaeval and vaguely threatening in his
relentless simplicity. Can it be that I inherit from a stone-age
ancestor both the fear and love of the bull-roarer?
Another bird that moves one in a very different way is the robin, of whom
it is hard to say whether he has more of tears or smiles in his
recitative. In comparison to the night-jar he seems like a civilised
human soul who has quite modern sorrows, and has half forgotten them in
quiet contentment with the autumn sunshine. The blackbird has a tinge of
the robin's sentiment, but it is over-borne by the glory of his song as a
whole, which is pure gold, like his beak.
The chaffinch is not an interesting person, and he is so numerous that
one soon becomes weary of him and his song. Let us hope that he
expresses his real nature in the building of his pretty nest rather than
in song. This must, I think, often happen, and to take an example from
human builders, it is not inconceivable that the architect of St. John's
College Chapel, Cambridge, may have sung delightfully. But there are
limits to one's faith, and personally I cannot imagine the desecrator of
Pembroke College in the same injured town of Cambridge practising any art
in a way that would please me.
To return to birds--the greenfinch is a pleasant singer, or perhaps a
conversationalist. I am never tired of hearing him repeat the word
"Squeese" as he sits hidden in the heavy shade of the summer elms. His
twinkling bell-note with its contented simplicity is also attractive.
His cousin, the bunting, makes remarks not unlike those of the
greenfinch; and he appears to address them by preference to the
travellers on dusty high roads, where he passes much of his time sitting
on telegraph wires. The anchorite yellow-hammer persistently declining
cheese with his bread is always pleasant. Professor Newton used to say
that the spring begins with the yellow-hammer's song. According to
Blomefield's _Calendar _{8} the average date in Cambridgeshire is
February 16, but he has been known to sing on January 30--rather a wintry
beginning for spring. I have never made up my mind as to what the
kitty-wren says or sings. He is always in a desperate hurry to get
through his piece, as if he were afraid of lagging behind the beat of
some invisible conductor. In consequence of this there is a want of
restraint, and a style that suggests a shy child gabbling a show bit of
poetry. But I repent these words for I love the kitty-wren.
There are a multitude of other bird-sounds which are pleasant to hear as
their turn comes round, for instance, the complaint of the wryneck, the
"cuckoo's mate," who seems to me to be querulously expressing his dislike
to my garden, which he tries year after year and deserts after a day or
two.
I have never heard that contented bird the quail, who should be a
wholesome lesson to all wrynecks. I should like to hear him as Schubert
has him:
"Sitzend im Grunen
Mit Halmen umhullt,"
and singing "Lobe Gott" all day in the rhythm with which the oboe praises
God in the Pastoral Symphony.
Another bird, whom I take for a contented fellow, is the green
woodpecker, for he goes through life laughing, but I am not quite sure
that I should like his taste in jokes. He is always associated in my
mind with a passage in a letter of my father's: "At last I fell fast
asleep on the grass, and awoke with a chorus of birds singing around me;
and squirrels running up the trees, and some woodpeckers laughing, and it
was as pleasant and rural a scene as ever I saw, and I did not care one
penny how any of the beasts or birds had been formed." {9}
There are many noises rather than notes which are most pleasant to hear.
The invisible industrious corncrake, whose persistent cry comes from
nowhere and everywhere at once. The harsh warning of the jay who seems
to say "Man! man!" as he skulks off when his wood is invaded. The rough
noise of the ox-eye sharpening his little saw, and many others.
Then I must not forget the noise of birds in flocks, ranging from the
familiar wrangle of sparrows noisily going to roost, to the mysterious
sound of great flights of birds migrating at night, one of the most
romantic of sounds, but to me untranslatable, since I do not know the
language of these wanderers.
I come now to human sounds. It was exciting to wake at 5 o'clock some
morning in June, and to learn by the sound of scythes being whetted that
the mowers had arrived, and that the hay harvest had actually begun. The
field had been a great sea of tall grasses, pink with sorrel and white
with dog-daisies, a sacred sea into which we might not enter. But now we
could at least follow the mowers, and watch the growth of the tracks made
by their shifting feet, and listen to the swish of the scythes as the
swathes of fallen grass and flowers also grew in length. There was
something military in their rhythm, and something relentless and
machine-like in their persistence. But our admiration was mixed with
pity from the time that one of them told us that after the first day's
mowing he was too tired to sleep. In later years another sound was
associated with haymaking, when in an Alpine meadow the group of resting
peasants were heard hammering the blades of their little pre-Raphaelite
scythes to flatten the dents made by stones hidden among the grass.
A well-remembered sound that came near the end of the harvest was the cry
of "Stand fast!" which was heard at intervals warning the man in the
cart, whose duty it was to arrange the pitched-up hay, that a move was to
be made. Why it was necessary to shout the warning so that it could be
heard a quarter of a mile away I cannot say. But its impressive effect
depended on its loud chant-like tone. This sound is connected with
recollections of riding in the empty hay-cart, from the sea-green stack
mysteriously growing in the corner of the field back to where hay waited
to be carted. The inside of the hay-cart was enchantingly polished, and
also full of hay-seed, which had a charm for me. The hay-making at Down
was a leisurely affair, with many women gossiping as they gently turned
the hay. There was, however, one man of whom we children were much
afraid, a fierce red-eyed old labourer who acted as foreman, and did not
hesitate to show that he thought us out of place in a hay-field.
One sound there was peculiar to Down,--I mean the sound of drawing water.
In that dry chalky country we depended for drinking-water on a deep well
from which it came up cold and pure in buckets. These were raised by a
wire rope wound on a spindle turned by a heavy fly-wheel, and it was the
monotonous song of the turning wheel that became so familiar to us. The
well-house, gloomily placed among laurel bushes, had a sort of terrifying
attraction for us, and I remember dropping pebbles and waiting--it seemed
ages--for them to fall into the water below. We believed the well to be
365 feet deep, also that this was the height of the dome of St. Paul's--I
have never tested the truth of either statement. The opening was roofed
in by a pair of hinged flaps, or doors, and I especially liked the moment
when the rising bucket crashed into the doors from below, throwing them
open with a brutal and roystering air, which one forgave it as having
made a long and dangerous journey up from the distant water. But the
best was when the empty bucket went down, and the fly-wheel spun round
till its spokes were invisible. Then was the time to remember the death
of a dog (called Dick) who was killed by jumping through the flying
wheel. I envied my elder brothers who could actually remember Dick: to
me he was only a tragic myth. I imagine that in hot dry weather more
water was drawn, or else that being more constantly out of doors we heard
more of it. It is at least certain that the sound of the well came to be
associated with peaceful days and happy weather in that dear garden.
Another sound I like to recall is connected with the memory of my father.
He daily took a certain number of turns round a little wood planted by
himself, and christened the Sandwalk. As he paced round it he struck his
heavy iron-shod walking-stick against the ground, and its rhythmical
click became a familiar sound that spoke of his presence near us, and was
associated with his constant sympathy in our pursuits. It is a sound
that seems to me to have lasted all those years that stretch from misty
childish days until his death. I am sure that all his children loved
that sound.
_February_, 1912.
II.
FRANCIS GALTON {13}
1822-1911
Francis Galton was born on February 16th, ninety-two years ago, and
to-day we are met together to remember him--a word that seems to me more
in tune with his nature than the more formal expression _commemorate_.
He disliked pomposity, but he seems to have loved little private
ceremonials. For instance, when he opened the first notebook in
preparation for his autobiographical _Memories_, he began page I with
Falstaff's words: "Lord, Lord, how subject we old men are to this vice of
lying"--an inverted appeal to truth which no man ever stood less in need
of. And again, at the foot of the very last page of his _Memories_ is a
drawing of _Galtonia candicans_, a little ceremony without words, a
hieroglyphic glorification of the honour paid him in giving his name to
this African plant.
Many persons, and even some reviewers, form their opinions of books by
reading half-a-dozen passages at random. I have been more scientific in
selecting the first and last pages, and from these I conclude that a
simple and kindly commemoration is not out of harmony with the genius of
this great and loveable man.
I should like to express my appreciation of the honour done me in asking
me to give the first Galton lecture. In many ways I am a bad choice,
since I have had no share in his science of eugenics, neither has my
research-work been directly connected with evolution. I can only hope
that in consideration of my delight in the fibre and flavour of Galton's
mind, with its youth, its charm of humour, and its ever-springing
originality and acuteness,--I say that I hope these considerations may
excuse me for having undertaken an office for which I am in so many ways
unfitted.
One of his most obvious characteristics was his love of method. I do not
mean methodicalness, but that he took delight in knowing how to do all
manner of things in the very best way. He also liked to teach his
methods to others. Those who never saw him, or even read his books, will
exclaim, "What a bore he must have been." One might as well call the
lightning a bore for explaining that the thunder was coming, or complain
of the match for boring the gunpowder as to the proper way of exploding.
With Galton's explanations there was a flash of clear words, a delightful
smile or gesture, which seemed to say: "That's all--don't let me take up
your time." Nobody was ever more decidedly the very antithesis of a bore
than Francis Galton.
He first appeared on the literary and scientific stage as a traveller,
geographer, and author of a book on South Africa (1853), and it was the
experience there gained that enabled him to write two years later, in
1855, that wonderful book, _The Art of Travel_. There he teaches such
vitally important things as how to find water, how to train oxen as pack
animals, to pitch a tent, to build a fire, to cook, and a thousand other
secrets.
He liked, of course, to be useful to weary and thirsty travellers, but he
was as much, or more, impelled by the love of method for its own sake.
He was in fact an artist in method. The same thing is shown in a letter
he wrote to Nature near the end of his life, explaining how to cut a cake
on scientific principles so that it shall not become stale. This again
was not so much a philanthropic desire that his fellow men should not
have dry cake, as delight in method.
When I re-read _The Art of Travel_ quite recently, I could not find his
method of preventing a donkey braying. My recollection is that,
observing a braying donkey with tail erect, he argued that if the tail
were forcibly kept down, as by tying a stone to it, the braying would not
occur. I certainly believe myself to have read or heard that this most
Galtonian plan succeeded.
Later in life he tried to make his unique knowledge of value to his
country. He writes: {15}
"The outbreak of the Crimean War showed the helplessness of our soldiers
in the most elementary matters of camp-life. Believing that something
could be done by myself towards removing this extraordinary and culpable
ignorance, I offered to give lectures on the subject, gratuitously, at
the then newly-founded camp at Aldershot."
He received no answer from the War Office, but a personal application to
Lord Palmerston led to his being installed. He speaks of a few officers
attending his course, and adds that the "rude teachings of the Crimean
War soon superseded" his own.
In relation to what I have been speaking of, I must here be allowed to
turn back to an earlier period of his life. In illustrating the
different dispositions of his sisters, both of whom were dear to him,
Galton writes:
"My eldest sister was just, my youngest merciful. When my bread was
buttered for me as a child, the former picked out the butter that filled
the big holes, the latter did not. Consequently I respected the former,
and loved the latter."
Have we not here an early appreciation of method, or must we merely class
the memory with the scene in "Great Expectations," where the terrifying
elder sister, Mrs. Joe, prepares bread and butter for her husband and for
Pip (her little brother) in an eminently just and disagreeable manner.
May I be allowed to add that a love of butter in the big holes is not
hereditary in all branches of the family; I should have loved the sister
who picked it out.
At a later stage in his boyhood Galton transferred his study of method
from his sisters to his schoolmasters. He describes what he suffered
from the absurd limitations (which still exist) in the education of
English boys, and chafed at the teaching he received. "Grammar," he
says, "and the dry rudiments of Latin and Greek were abhorrent to me, for
there seemed so little sense in them." He suffered in fact like his
cousin, Charles Darwin, who groaned over the classics at Shrewsbury
School, and forgot what he learned, even to some of the Greek letters, by
the time he was nineteen.
In 1838, when Galton was sixteen years of age, he became an indoor pupil
at the Birmingham General Hospital. Here the education was at any rate
practical enough, and to this coddled generation it sounds a rough
introduction to medicine. He had to prepare tinctures, extracts,
decoctions, and learned to make pills by hand--a slow enough process. In
later life, when he saw a pill-making machine at work, it must have been
his boyish memories which inspired the characteristic calculation that if
a grandmotherly Government possessed forty-five of these engines, it
could supply each inhabitant of the British Isles with one pill per diem.
It was in the surgery that he had most experience; he and the other
indoor pupils were called up at all hours to dress burns, to patch broken
heads, and reduce dislocations, with, as it seems, very little
instruction. It was doubtless a fine bit of education in self-reliance,
and he must have learned much that was of use in his South African
travels. Whether as a student of method he approved of his rough and
ready education is not quite clear. His genius for experiment, or rather
that priceless capacity for extracting unexpected conclusions from
experience, comes out in his account of a case in the Birmingham
Hospital. An injured drayman was brought in dead drunk, and underwent
amputation of the legs without any signs of feeling pain. This set
Galton wondering whether patients might not with advantage be made drunk
before operations--a query which was to be happily answered by the
discovery of anaesthetics.
Another characteristic event was his attempt to learn the properties of
all the drugs in the pharmacopoeia by personal experience. He determined
to dose himself alphabetically, but got no further than C., for the
effects of croton oil put a stop to his thirst for first-hand knowledge.
We must pass over his time at King's College, London, where, as he sat at
lecture, he could see the "sails of the lighters moving in sunshine on
the Thames," a vision which stirred his blood with a longing for
adventure, and which, as he characteristically noticed, always occurred
when the weather-cock on the Horse Guards showed that the south-west wind
was blowing.
We must, in like manner, skip his undergraduate days at Trinity,
Cambridge. We thus arrive by a devious route at the period when he
returned a traveller and geographer of recognized merit, and began the
work with which he was practically connected for many years, as a member
of the Meteorological Committee. His best-known contribution in the
science was in a paper read before the Royal Society in 1862, where his
discovery of the anticyclone was first described; but he also had a good
deal to do with the printing and publishing of the now familiar weather
charts. Meteorology takes us from 1861 to 1863, that is nearly to 1865,
when his first paper on heredity appeared, which was at the same time his
first paper on hereditary genius. This line of research was to form his
chief claim to celebrity and must be separately treated.
Meanwhile I wish to say something of his love of experiment, which is a
branch of his devotion to method. We know something of the more
entertaining of his inquiries from his delightful book of _Memories_, yet
I cannot but fear that he has left out many experiments even stranger
than those he publishes. My father had a special affection for what in
his own case he called "Fool's experiments." These are what, I am
afraid, Galton may have omitted. Still there are records of some
delightful lines of work. He is probably the only man who ever attempted
to solve by experiment the problem of free will and determinism. He
limited his inquiry to the question--whether there exists in human
affairs such a thing as an "uncaused and creative action." The
experiment, or rather self-observation, was carried on (1879) for six
weeks, almost continuously, and "off and on for many subsequent months."
He found that with practice he could nearly always trace the
"straightforward causation" of a given action, which at first seemed to
have been performed "through a creative act, or by inspiration."
Then there was his attempt to experience the feelings of the insane.
"The method tried was to invest everything I met, whether human, animal,
or inanimate, with the imaginary attributes of a spy." The trial was
only too successful; by the time he had walked 1.5 miles to the cab-stand
at the east end of the Green Park "every horse in the stand seemed
watching" him, "either with pricked ears, or disguising its espionage."
He adds that hours passed before this uncanny sensation wore off. On
another occasion he managed to create in his mind the feelings of a
savage for his idol, the idol in his own case being a picture of Mr.
Punch.
These experiments seem to me very characteristic of the man in their
originality, their humour, and their unexpected measure of success, for
personally, I should have prophesied failure in all. They have a special
bearing on Galton's belief that a quasi-religious enthusiasm for eugenics
may be built up. I have sometimes wondered that he should believe this
great change so feasible, but I understand how he came to think so when I
read of his strange power of impressing beliefs on himself, with such
force as to leave a trail of discomfort in the mind after the
make-believe had ceased.
These and similar trials were, I think, made in relation to his desire to
weigh and measure human faculty in a broad sense. I remember his telling
me of his experiments on the mind of the British cabman. His method was
to use alternately two different forms of the address to which he wished
to go. Thus on Monday he would tell the man to drive him home to 42,
Rutland Gate, on Tuesday he would say, "Rutland Gate, 42," and so on. My
recollection is that the cabmen understood more quickly the familiar
formula in which the number precedes the name of the street.
There was also a characteristic experiment or inquiry into the intensity
of boredom in a lecture audience, by counting the number of fidgets per
man per minute. In this case to avoid the open use of a watch, he
estimated time by the number of his own breaths, "of which there are
fifteen in a minute." I hope my brother {21} will forgive my adding that
he found the Royal Geographical Society meetings good hunting-ground for
fidgets, for as Francis Galton remarks, "Even there, dull memoirs are
occasionally read."
Nor must I forget his plan of marking, by means of a hidden apparatus,
the beauty of the women he met in the streets of different towns. He
classified them as pretty, ugly, and indifferent; in this beauty
competition London came out at the top; Aberdeen, I regret to say, was at
the bottom.
But in considering the measurement of human faculty we have got quite out
of any reasonably chronological sequence, for the book bearing that title
appeared in 1883. But the estimation of human characteristics,
especially in relation to heredity, was in Galton's mind several years
earlier, and in 1865 he wrote the two papers in _Macmillan's Magazine_
which contain the germs of his later work on heredity and eugenics. It
is unfortunate that the research on heredity, together with its practical
application to human welfare in the new science of eugenics, should not
have more space given to it in his autobiographical _Memories_; there are
but thirty-seven pages--or 11 per cent. of the whole book. The specific
importance of the subjects here dealt with is so great that these
thirty-seven pages outweigh all the rest of the book. We should like to
have had a fuller account by the author of this remarkable work of 1865.
He does, however, tell us--and it is a very striking statement--that the
two articles "expressed then, as clearly as I can do now, the leading
principles of Eugenics."
The chief point in which he came to differ from the _Macmillan_ articles
was that he was then "too much disposed to think of marriage under some
regulation, and not enough of the effects of self-interest and of social
and religious sentiment." I imagine that the pendulum has now swung the
other way, and that one of the most hopeful and practical schemes is the
prevention of marriage among habitual criminals and the feeble-minded.
Galton attributes his work in heredity in some measure to the publication
of the _Origin of Species_, which, he says, "made a marked epoch" in his
"mental development, as it did in that of human thought generally."
That Galton personally felt no difficulty in assimilating the new
doctrine, he characteristically ascribes to a "bent of mind that both its
illustrious author" and himself had "inherited from" their "common
grandfather, Dr. Erasmus Darwin." But in our day the name of Galton is
intimately connected in our minds with the science of heredity, and we
forget that he, like lesser men, was a mine fired by the _Origin_. He
was "encouraged," he says, "by the new views to pursue many inquiries
which had long interested" him "which clustered round the central topics
of heredity." This was the charge with which the mine had been
loaded--the _Origin_ was the fuse.
When that book was published in 1859, nearly everyone here to-night must
have been too young to know anything of the great change in the colour of
human thought which was ushered in. There are more who may remember how
twelve years later, when the _Descent of Man_ came out, there was still
plenty of clerical and other forms of foolish bitterness. But a man
needs to have been in the full swing of mental activity in 1859 to
perceive the greatness of the change due to the _Origin of Species_.
His two papers in _Macmillan's Magazine_, 1865 (Vol. XII., pp. 157 and
318), seem to me very remarkable, and, as I have said, they are passed
over too lightly by the author in his _Memories_ (p. 310). They contain
a statistical proof of the inheritance of intellectual and moral
qualities. {23} And those who would allow the truth of this statement
must further agree that it is the first statistical demonstration of this
important fact that the world has seen. And he insists that the whole
spiritual nature of man is heritable, so that in his opinion there are no
traces of that new element, "specially fashioned in Heaven," which (he
says) is commonly believed to be given to a baby at its birth.
The paper contains a very interesting discussion on the development of
social virtues by natural selection. He gives, too, a characteristic
explanation of that human attribute commonly known as Original Sin, the
quality, in fact, which makes men yield to base desires against and in
spite of their sense of what is right. He says {24} that here "the
development of our nature under Darwin's law of natural selection has not
yet overtaken the development of our religious civilisation." It may be
more briefly described as the conflict between the individual desires
with the tribal instincts. It must be remembered that for all this
discussion Galton had no _Descent of Man_ to guide him.
I shall come back later to his clear and courageous statement of eugenics
in 1865. Meanwhile I must speak of heredity, a word, by the way,
introduced by Galton, and for which he seems to have been taken to task.
With regard to the machinery of reproduction the essay is remarkable for
containing what is practically identical with Weismann's continuity of
the germ-cell, and Galton's priority is acknowledged by that author. But
in science the credit goes to the man who convinces the world, not to the
man to whom the idea first occurs. Not the man who finds a grain of new
and precious quality, but to him who sows it, reaps it, grinds it and
feeds the world on it. This is true of this very _Macmillan's Magazine_
article. Who would know of these admirable views on Hereditary Genius
and Eugenics, if this were Galton's only utterance? This is the grain
which has increased and multiplied: and it is to-day familiar nutriment,
and is now assiduously cultivated by the Eugenics Education Society. But
if _Natural Inheritance_, and _Hereditary Genius_ had not been written;
if the papers on eugenics had not appeared, and especially if he had not
convinced the world of his seriousness by creating a eugenic foundation
at University College, where his friend Professor Karl Pearson carries on
the Galtonian traditions--why then the paper in _Macmillan_ would have
counted for very little. But it was not quite unnoticed. By my father
it is referred to in the _Variation of Animals and Plants under
Domestication_. Galton was encouraged and reassured by Darwin's
appreciation of his work: his words in _Hereditary Genius_ {25} are, "I
feel assured that, inasmuch as what I then wrote was sufficient to earn
the acceptance of Mr. Darwin . . . the increased amount of evidence
submitted in the present volume is not likely to be gainsaid." He was
characteristically generous in owning his debt to the author of the
_Origin of Species_, and characteristically modest in the value he
ascribed to my father's words.
The book on Hereditary Genius strikes me as most impressive. It seems as
though the man whom the world had agreed to honour as an admirable and
indeed a brilliant worker in geography and meteorology had suddenly grown
big. He shows himself to have the power of sustaining a weighty argument
in strong and temperate phrase, speaking as judge rather than advocate,
and to have definitely taken rank with Darwin, Lyell, Hooker and Huxley,
men whose pens have dinted the world, leaving their ineffaceable mark on
the road trodden by the march of science.
When I was working at the _Life and Letters of Charles Darwin_, I
naturally asked Mr. Galton for leave to publish the letters he had
received from my father. But he would not agree. Mr. Darwin, he said,
had spoken far too kindly of his work, and he preferred to keep the
praise to himself. But later, when he wrote his _Memories_, {26a} he
fortunately realised that it is wiser to think of the value to the world
of such documents, than of private likes or dislikes. The letter my
father wrote about _Hereditary Genius_ which Galton says "made him most
happy" begins:
"I have only read about 50 pages of your book . . . but I must exhale
myself, else something will go wrong in my inside, I do not think I ever
in all my life read anything more interesting and original." {26b}
In reading this great book it is, I think, impossible to doubt the
strength of the work. The quiet relentless way in which his territory is
pegged out, and the clear wisdom with which the terms of the new science
are defined, are equally impressive. And for lighter enjoyment his
illustrations are to be recommended. He has to settle precisely what he
means by a man being _eminent_ or _illustrious_ before he can begin to
ask--are these qualities hereditary? An eminent man is one in four
thousand, and to make clear what this implies, he writes: "On the most
brilliant of starlight nights there are never so many as 4000 stars
visible to the naked eye at the same time; yet we feel it to be an
extraordinary distinction to a star to be accounted as the brightest in
the sky." {27a} If we could imagine that each new night shows us a fresh
set of stars, we might speculate as to how many nights we should watch
the sky before we found one bright enough for a Galton.
In the same way he tries to make us see a million, because in that number
there is but one illustrious man. He worked it out in Bushey Park, where
he had gone to see the horse-chestnuts in flower, and came to the
astonishing conclusion that, taking one half only of the avenue and the
flowers visible on the sunny side of that row, it would require 10 miles
of avenue to give 1,000,000 spikes of blossom.
Later he defines _mediocrity_ in a way not very flattering to those, who,
like myself, live in the country. Mediocrity {27b} then "defines the
intellectual power found in most provincial gatherings, because the
attractions of a more stirring life in the metropolis and elsewhere are
apt to draw away the abler classes of men, and the silly and imbecile do
not take a part in the gatherings." On this last point, by the way, I am
not convinced. The research on the heredity of mental and moral
characters leads naturally to eugenics, as in the 'Macmillan' paper of
1865. But before dealing with this I must say a few words about what, in
the opinion of some, is Galton's chief claim to eminence--the study of
heredity as a whole. There is no doubt that he was the first to treat
thoroughly and in a strict statistical method, the steps by which one
generation passes into the next. He was pre-eminently a lover of
statistics, he was indeed what Goschen called himself, "a passionate
statistician."
He used Gauss's Law of Error, which Quetelet had already applied to human
measurements. "The primary objects," he says, "of the Gaussian Law of
Error were exactly opposed, in one sense to those to which I applied
them. They were to get rid of, or to provide, a just allowance for
errors. But these errors or deviations were the very things I wanted to
preserve and to know about."
This conception of variation impressed him deeply, so that he remembered
the exact spot in the grounds of Naworth Castle where it first occurred
to him "that the laws of heredity {28} were solely concerned with
deviations expressed in statistical units."
What may be called the final result of Galton's work in heredity is, I
imagine, his _ancestral law_, namely that "the average contribution of
each parent" to its offspring is one quarter, or in other words, that
half of the qualities of the child can be accounted for when we know its
father and mother. In the same way the four grandparents together
contribute one quarter, and so on. He illustrates this by calculating
how much Norman blood a man has who descends from a Baron of William the
Conqueror's. Assuming that the Baron weighed 14 stone, his descendant's
share in him is represented by 1/50 grain. {29}
This side of Galton's work is, in the judgment of many, his greatest
claim to distinction as a master in the science of heredity. How far
this is so I shall not attempt to pronounce. It is possibly still too
soon to do so. Nevertheless, it seems to me that Mendelism, the main
facts of which are no longer in dispute, will compel the world (if it has
not already done so) to look at variation in a very different way to that
of Galton. The Mendelian does not, and never will, look at variation
merely as a "deviation expressed in statistical units." Nor can he
accept the ancestral law, because he has convinced himself that some
ancestors contribute nothing in regard to certain characters.
The contrast between Galtonism and Mendelism may be illustrated by an
example, which, if not a strict analogy, has in it something
illuminating, especially for those who do not know too much of the
subject. Galton seems to me like a mediaeval chemist, while Mendel is a
modern one. Galton can observe, or can follow the changes that occur
when two compounds are mixed. But he knows nothing of the mechanism of
what occurs. But the Mendelian is like a modern chemist who calls the
chemical elements to his aid, and is able to express the result of the
experiment in terms of these elements. This is an enormous advantage,
and if my analogy is to be trusted, it would seem as though a progressive
study of heredity must necessarily be on Mendelian lines.
But it obviously does not follow that the laborious and skilful work of
Galton and his school is wasted. Those who wish to have made plain to
them how Biometrics may illuminate a problem which cannot as yet be
solved in Mendelian fashion, should read Dr. Schuster's most interesting
book on eugenics. I am thinking especially of the question as to the
heredity of tuberculosis and cancer. The relation between Galtonism and
Mendelism is also well and temperately discussed in the late Mr. Lock's
_Recent Progress in the Study of Variation_, 1906.
But it is time to speak of Galton as a eugenist--on which if we look to
the distant future his fame will rest. For no one can doubt that the
science of eugenics must become a great and beneficent force in the
evolution of man.
We must be persistent in urging its value, but we must also be patient.
We should remember how young is the subject. As recently as 1901 Galton
was, in his Huxley Lecture, compelled to speak of eugenics in these
terms: {30}
"It has not hitherto been approached along the ways that recent knowledge
has laid open, and it occupies in consequence a less dignified position
in scientific estimation than it might. It is smiled at as most
desirable in itself, and possibly worthy of academic discussion, but
absolutely out of the question as a practical problem." After explaining
that the object of his discourse was to "show cause for a different
opinion," he goes on with what, in his restrained style, is strong
language: "I shall show that our knowledge is already sufficient to
justify the pursuit of this perhaps the grandest of all objects." {31a}
At the close of the lecture he speaks out as to the difficulties and the
pre-eminent value of eugenics, and once more of the oppressive "magnitude
of the enquiry."
No one who reads this lecture of Sir Francis Galton's is likely to let
eugenics go with a smile, and a remark that it is not a practical
problem. It is one of the functions of the Eugenics Education Society to
spread the sanely scientific views here set forth by Galton, and as far
as I am able to judge, the Society has and is doing sound work in this
direction.
In another essay, {31b} Galton discusses the meaning of the 'eu' in
eugenics in a characteristic way. He imagines an attempt among the
animals in the Zoological Gardens to establish a code of absolute
morality. With customary love of detail he supposes the inquiry to be
undertaken by some animal, such as a sparrow or a rat, which is
intelligent and has easy access to all the cages, and is therefore able
to collect opinions. There would be strongly pronounced differences
between the carnivorous animals and those which form their natural prey.
There would be a general agreement as to maternal affection, though
fishes and the cuckoo would laugh at it. But all would agree on some
eugenic principles: That it is better to be healthy and vigorous than
sickly and weak--well-fitted for their part in life rather than the
reverse--in fact, good specimens of their kind whatever that kind may be.
Sir Francis Galton goes on to give a list of qualities that "nearly every
one except cranks would take into account in picking out the best
specimens of his class." The list includes "health, energy, ability,
manliness and courteous disposition." {32a} I wish he had thought of
eugenic mothers, and had translated manliness into the feminine
equivalents of courage and endurance. When I first read this list it
struck me at once how highly distinguished was Galton himself in all
these qualities. As we dwell on the qualities one by one, they seem to
call up echoes from the image we have of his character. "Ability,
manliness, and courteous disposition," how strong these were in him! I
cannot help feeling that he might have added one more quality from his
own treasure-house, namely, a sense of humour, which is so priceless an
antiseptic to sentimentality, and was markedly present in his character.
In this same lecture {32b} Galton sums up the stages in the development
of eugenics. (1) "It must be made familiar as an academic question."
(2) As a practical subject worthy of serious consideration. (3) It must
be "introduced into the national conscience, like a new religion." He
recapitulates in an eloquent phrase: "It has, indeed, strong claims to
become an orthodox religious tenet of the future, for Eugenics cooperates
with the workings of Nature, by securing that humanity shall be
represented by the fittest races. What Nature does blindly, slowly, and
ruthlessly, man may do providently, quickly, and kindly."
Here we see the future of eugenics marked out for us, and the last
sentence might well serve as a motto for this Society. How are we to
work for the cause?
It is true that our opinions are formed by the daily papers, and our
actions as a nation are determined by political parties which come and go
largely by chance. But however our opinions originate, if they are
strongly and persistently urged by a large majority of Englishmen, great
changes in the manner of human life may be effected. Persistence is the
great thing in all reforms: in the words of my father's favourite
quotation--"It's dogged as does it." Francis Galton has been temperately
persistent in a marked degree. His caution and wisdom are illustrated by
the dates of his writings on eugenics and heredity, which placed in order
suggest a regiment relentlessly advancing, not a bunch of heroes rushing
on a breach:--
Two papers in 'Macmillan's Magazine' 1865
Hereditary Genius 1869
'Fraser's Magazine' 1873
Human Faculty (word 'Eugenics' first employed) 1884
Natural Inheritance 1889
Huxley Lecture 1901
Sociological Society Papers 1905
`Memories 1908
His temperate advance is all the more striking when we remember the fiery
impatience with which in _Hereditary Genius_ he spoke of the harm done by
the Church in ordaining that the intellectuals, the literary, and the
sensitive should be celibates, and of the wholesale slaughter by the Holy
Inquisition of the courageous and clear minded who dared to think for
themselves.
From the first he had the support of Charles Darwin, who never wavered in
his admiration of Galton's purpose, though he had doubts about the
practicality of reform. His hesitation in regard to eugenic method is
expressed with a wise proviso as to future possibilities: "I have lately
been led," he says, "to reflect a little . . . on the artificial checks,
but doubt greatly whether such would be advantageous to the world at
large at present, however it may be in the distant future." {34a} In the
first edition of the _Descent of Man_ (1874), {34b} he distinctly gives
his adherence to the eugenic idea by his assertion that man might by
selection do something for the moral and physical qualities of the race.
It is a great thing that this Society should have had Francis Galton for
its Honorary President. It entitles us to feel assured that in following
the line of action marked out for ourselves we are on the right track,
and that in the difficult pioneer work of helping the English public to
realise the deadly need of eugenic reform we are following in Galton's
steps. We are also so fortunate as to have received encouragement and
help at the hands of some of the leaders in the science of heredity,
Weismann, Yves Delage, Ray Lankester, the late Adam Sedgwick, Poulton,
Bateson, and others.
Galton says somewhere {35} that great men have long boyhoods. This was
certainly true of him, though I should rather describe as youthful the
delightful qualities that never faded out of his nature. It is, I
believe, the correct thing to speak of the "golden dreams of youth," and
if by this hackneyed phrase we mean a keenly imaginative outlook, a
hopefulness with a certain dash about it, a generous courage--tinged with
romance--then Francis Galton had undying youth. And this makes his
seriously measured progress in eugenics all the more worthy of our
admiration.
In one of the Macmillan articles he wrote: "Many plan for that which they
can never live to see. At the hour of death they are still planning."
It was thus that Francis Galton died, and as year after year we meet
together on February 16th, let us think of him and his plannings with
affection and respect.
III
THE MOVEMENTS OF PLANTS {36}
It is sometimes asserted that the power of movement is a character
distinguishing animals from plants. This statement arises to some extent
from an obvious confusion of thought. Trees are stationary, they are
rooted to one spot, but they are not therefore motionless. We think them
so because our eyes are dull--a fault curable with the help of a
microscope. And when we get into the land of magnification, where the
little looks big and the slow looks quick, we see such evidence of
movement that we wonder not to hear as well as see the stream of life
that flows before our eyes.
In speaking of the cells of which plants are built, Huxley said that a
plant is "an animal enclosed in a wooden box." It is this prisoner, the
living protoplasm, that we may watch pacing round its prison walls. And
we may see it stop as though frightened at our rough usage, and then,
after a hesitating twitch or two, we see it recover and once more flow
round the cell. Or we can watch under the microscope minute
free-swimming plants rushing across the field of view, all one way, like
a flock of little green sheep that we can drive to and fro with a ray of
light for a sheep-dog.
But I am not going to deal with microscopic matters, but rather with
things on a bigger scale which can be seen with the naked eye. I will
begin by trying to show that very obvious movements are to be seen in
every kitchen garden, or in every garret window, where a scarlet runner
is grown for its red flowers' sake.
In a scarlet runner the shoot is not completely vertical, but bends over
to one side. To record the movements of the plant a series of
photographs may be taken vertically from above the plant, so that the end
of the shoot shows like the hand of a watch against a sort of clock-face
on which the points of the compass are marked. Such photographs show how
the shoot swings round in its instinctive search for another stick to
climb.
This well-known movement is performed by a co-ordinated series of
curvatures, the exact nature of which need not trouble us now. Let us
rather consider the less obvious power of co-ordination which enables a
plant to grow upwards in a straight line. Think of a forest of pine
trees, hundreds of thousands of them, all growing vertically up towards
the sky. Here is a clear case of movement, for the leading shoots were
once but a few inches from the ground, and now they are crawling along
vertical lines 100 feet up in the air. It may be said that this is mere
increase in size, not movement in the ordinary sense. But it may be made
plain that the trees could not grow in this way had they not a power of
curvature, to which the term _movement_ cannot be refused.
As it is not easy to experiment on pine trees we may use a pot of mustard
seedlings, which represents in miniature a forest of vertical stems. Now
suppose the flower-pot upset and left lying on its side for a few hours:
the seedlings will be found to have all recovered the vertical position,
and they have done so by a bend which is just as much a case of movement
as the flexure of a man's arm, though it is effected by a very different
mechanism. Not everyone realises how rapid this movement is. Fig. 2 is
from a diagram made in the ordinary course of class-work at Cambridge,
and illustrates this point. A shoot of Valerian was placed horizontally
at 2.17, and a black line painted like a silhouette on a vertical sheet
of glass to record its position at 2.30; similar lines were painted at
intervals, forming a record of fairly rapid movement. If greater
delicacy of observation had been practised, it would have been easy to
show that the plant begins to curve up within a few minutes of being
placed horizontally.
It is a remarkable fact that the plant should be stimulated, or stirred
up, to a definite curvature by merely placing it horizontally. The
curvature tends to bring the plant into the upright position, and when
the whole stem has reached the vertical, the stimulus ceases to exist.
It is as though the plant were in a condition of content when vertical,
and of discontent in any other position, and as though the discontent
expressed itself in curvature.
But the plant does not gain the vertical by a single continuous
curvature; at first it overdoes the thing (see Fig. 2), and the end of
the shoot may pass beyond the vertical by 20-30 degrees. But this new
position, inasmuch as it is not vertical, originates a new stimulus, and
the new curvature which follows brings the shoot back towards the upright
position. It may again overshoot the mark, but by repeated corrections
it finally attains the normal upright posture.
It is this power of correcting the line of growth whenever it deviates
from the upright that enables the pine tree to grow straight upwards.
And this is what I meant when I said that its habit of growth depends on
regulated curvature, to which no one can refuse the name of movement.
[Picture: Fig. 2.--A Valerian stem curving geotropically]
The pine and the seedling have, in fact, a wonderful kind of
sensitiveness--a sensitiveness to the force of gravity. To those
accustomed to think of Mimosa as the sensitive plant _par excellence_ my
words may sound strange. But the sensitiveness of Mimosa is crude by
comparison with that of the seedling. A plant with a perception of the
position of the centre of the earth and a power of growing along the line
so perceived is a much greater miracle than a leaf that closes its
leaflets when burnt or cut or shaken.
I shall show that certain parts of the plant have the special quality of
the perception of gravitation, but we are at present ignorant of how the
act of perception is effected. We know something of the machinery of
hearing or vision in animals, but in plants we can only guess that when a
cell is placed horizontally a resulting change of pressure on the
protoplasm produces that loss of equilibrium which is translated into
curvature. It is, however, probable that Nemec and Haberlandt are right,
and that the stimulus depends on the pressure of solid particles, _e.g._
starch-grains, on the protoplasm. {40}
The use of this gravitational sensitiveness is clear enough. It is to
the pine tree what a plumbline is to the builder, for neither plant nor
man can build high unless he builds straight. A man has a general
perception of the verticalness of his body and of surrounding objects,
but he does not trust to this sense in placing brick on brick to make a
house. He uses a plumb-line which tells him through his eye the precise
line along which he must pile his bricks. The tree has also to pile one
over another the cells or chambers in which its protoplasmic body lives,
and this too must be done along a vertical line; but the plant is guided
by the sensitiveness to gravity of which I have spoken.
It must be clearly understood that gravity does not act directly on the
growth of plants. It does not act as a magnet acts on iron, or to take a
better example, it does not simply act as gravity acts on the plumb-line
in which the string is kept in a vertical line by the weight. It might
be supposed that in some occult way the stem was mechanically kept
straight like the string, and this indeed was the view formerly held
about such roots as grow straight down into the earth. But it is not so;
the thing is not explicable mechanically. Gravitation is nothing more
than a sign-post or signal to the plant--a signal which the plant
interprets in the way best suited to its success in the struggle for
life, just as what we see or hear gives us signals of changes in the
exterior world by which we regulate our conduct.
It may be said that this is hard to prove, and indeed, like other
biological theories, it can only be shown to be true by its explaining a
number of facts. It is interesting to try to explain the facts without
the assumption in question. If gravity does not act indirectly as a
signal it must act directly; and we must find a reason why, in the case
of the mustard seedling above referred to, the stem has grown up and the
root down. There is absolutely nothing in their structure or manner of
growth to help us to see why this difference of behaviour under identical
conditions should exist. And if, instead of placing the mustard seedling
in the dark we had grown it near the window, {41} we should have come
across another remarkable phenomenon, namely, that the stem grows
towards, the root away from, the light--and this is equally inexplicable
on a mechanical basis.
But it may be urged that it is not fair to compare a root and a stem
which are structurally unlike. Let us, therefore, keep to roots. When
the root of a bean has grown vertically down into the soil for some
distance it begins to bud forth into side roots. These are exactly like
the primary root from which they spring; there is no difference in
structure or in machinery of growth. Yet the secondary roots do not grow
vertically down, but obliquely, or in some cases horizontally. There is
one more striking fact about the roots of the bean. The secondary, like
the primary roots, give off branches, and these--the tertiaries--behave
differently from both the elder generations of roots. For instead of
directing themselves vertically or horizontally, they simply treat the
force of gravity with contempt and grow where fancy leads them. The
point on which I wish to insist is, that it is impossible to explain on
any theory of the _direct_ action of gravity why the three orders of
roots have three distinct modes of growth. They may remind us of three
generations, grandfather, father, and son, all of one blood and yet
behaving towards the universe in three distinct ways--a fact not unknown
in human society.
On the other hand, it would not be difficult to show that the behaviour
of the three orders of roots is well suited to the plant's needs, and
therefore we can understand how the power of reacting in three different
ways to the same signal has been evolved. The main root takes the
shortest course to the deeper layers of earth; the four or five ranks of
secondary roots divide the world between them and push forth all round,
keeping slightly below the horizontal; the tertiaries take it for granted
that their predecessors have done the usual thing, and that they can
satisfactorily occupy the spaces left among their elders by random
growth. The fact that the tertiary roots have no specialised
sensitiveness of gravitation shows that their unregulated growth is good
enough for the necessities of the case. For among organised beings
necessity is the mother of development, and what their brethren of second
rank have developed they too could assuredly have gained. To this point
of view I shall return, but first I should like to give a few more
instances of actions carried out in response to the signal of gravity;
and these examples shall be from stem-structures.
The ripe flower-heads of a clover (_T. subterraneum_) bury themselves in
the ground, thus effectually sowing their own seeds, and they are guided
to the ground by their unusual capacity of curving down and directing
themselves like a primary root towards the centre of the earth.
Other flower-stalks are guided by gravitation for quite different
purposes. Take, for instance, a common narcissus. In the young
condition there is a straight shaft ending in a pointed flower-bud; but
as the flower opens the stalk bends close to the top and brings the
flower-tube into a roughly horizontal position, where it shows off its
brightly coloured crown to the insects that visit it. The flowers are
guided to the right position by the gravitational sense, and they
increase or diminish the angular bend in their stalk till the right
position is attained, as shown in Fig. 3.
All these cases of plants executing certain useful curvatures, which
occur when the plant is displaced as regards the vertical, and cease when
the habitual, relation is reached, all these, I say, seem to me only
explicable on the theory that gravitation does not act as a mechanical
influence, but as a signal which the plant may neglect entirely, or, if
it notices, may interpret in any way; that is, it may grow along the
indicated line in either direction or across it at any angle. It may be
said that this is no explanation at all, that it only amounts to saying
that the plant can do as it chooses. I have no objection to this, if the
meaning of the word 'choice' be defined.
I am now going to deal with the subject of movement from a somewhat
different point of view, namely, with the object of showing that it is
possible to discover the part of the plant which reads the signal: and
this is not necessarily the part that executes the correlated movement.
In the reflex movement of an animal (for instance, a cough produced by a
crumb going the wrong way), we distinguish the irritation of the throat
and the violent action of the muscles of the chest and abdomen; and
further, the nervous machinery by which the stimulus is reflected or
switched on, by way of the central nervous system, from the throat to the
muscles concerned in coughing. In the plant, too, if we are to compare
its movements to the reflexes of animals (as has been done by Czapek), we
must distinguish a region of percipience, another of motility, and the
transmission of an influence from the percipient to the motor region.
Transmission of a stimulus has long been known in _Mimosa_, but, in the
far more important curvatures which we are now considering, it was not
known to [Picture: Narcissus flowers] exist before the publication of the
_Power of Movement in Plants_. There is an experiment of Rothert's {45}
which we make in class-work at Cambridge, and which only differs from my
father's classical experiment in the fact that a much more perfectly
adapted plant is employed. The plant in question is a grass, _Setaria_,
which has a remarkable form of seedling. When the grain germinates it
does not send up a simple cylindrical sprout like an oat, but a delicate
stem terminating in a pointed swollen part which looks like a little
spear-head. When a group of _Setarias_ is illuminated from one side they
bend strongly over, with their spearheads all pointing straight at the
light. The spearheads do not bend; the whole movement is carried out by
the stalk on which the head is supported. And what is remarkable is,
that the spear-head and not the stalk perceives the light. This is
easily proved by covering the heads of a few _Setarias_ with opaque caps.
For the result is that the blindfolded seedlings remain vertical while
their companions are pointing to the light. Thus the part which bends,
is unaffected by illumination, and the part which _is_ affected does not
bend. The spear-head is the percipient organ, the shaft or stalk is the
motor region, and from head to shaft an influence has clearly been
transmitted.
My father and I made an attempt to prove the same thing for the
gravitation-sense of roots, that is, to prove that the tip of the root is
the region in which the force of gravity is perceived by the plant. Our
method of proof does not hold good, but our conclusions are true after
all. When gravitation is the stimulus, the experiment is much more
difficult than when light is in question, because now that fairy
godmothers are extinct we must not hope for a substance opaque to
gravitation, a substance with which we might shelter the root-tips from
the force of gravity as the tips of the _Setaria_ seedlings were
sheltered from light.
The plan adopted by us was simply to cut off the extreme tip of the
roots, and fortunately (or unfortunately) the result was just what was
expected--the tipless roots had lost the sense of gravitation, and were
unable to curve downwards towards the centre of the earth. It was
natural to believe that the tipless roots failed to bend because their
sense-organs--their percipient parts--had been removed. As a matter of
fact they had been removed, but it was fairly objected that the operation
of removing the delicate tissues at the tip of the root is a severe one,
and that the roots which refused to grow downwards were suffering from
shock, and not from the absence of their sense-organs.