NA TURE 



329 



THURSDAY, FEBRUARY 15, 1877 



DARWIN ON FERTILISATION 



The Effects of Cross- and Self-Fertilisation in the 

 Vegetable Kingdo7n. By Charles Darwin, M. A., F.R.S., 

 &c. (London : John Murray, 1876.) 



FEW as arc the students of vegetable physiology 

 in this country, it is very far from a mere 

 boast to say that, with Mr. Darwin's aid, we have 

 no reason to shrink from comparing English work in 

 this subject with that done abroad. Mr. Darwin has 

 sometimes lamented that he is not a botanist, yet it would 

 be difficult to name any scientific man with an accepted 

 claim to that description who could point to more valuable 

 botanical work than his studies of heterostyled plants, 

 the fertilisation of orchids, and the habits of climbing and 

 insectivorous plants. As to the present volume, there is 

 no risk whatever in stating that it at once takes and will 

 always retain a classical position in botanical literature. 

 And when one considers that these are not the only 

 things which have come during late years from the same 

 apparently inexhaustible treasury, and when one remem- 

 bers also that the great student who has filled it has 

 throughout struggled with difficulties which would have 

 effectually quenched the energy of most men, one may 

 allow oneself to wonder whether Mr. Darwin's own 

 scientific activity is not itself a more than remarkable 

 biological problem. 



There can be no doubt that the publication of the 

 present work is extremely opportune. An enormous body 

 of observations, of which a great part have been brought 

 together by Dr. Hermann Miiller, have solidly confirmed 

 the well-known induction stated by Mr. Darwin in 1862, 

 that "nature abhors perpetual self- fertilisation." Most 

 persons who have studied the subject have been satis- 

 fied that the facts safely covered the conclusion that the 

 varied adaptive contrivances in flowers really had for 

 their object the prevention of self- and the promotion of 

 cross-fertilisation, even if nature chose to preserve an 

 impregnable silence as to the reason of her abhorrence 

 of the former process. There have not, however, been 

 wanting those who have attempted to explain away the 

 significance of all that had been stated. Not seeing the 

 mischief of self- fertilisation, they have hastily assumed 

 that it had none, and thence have arrived at the conclu- 

 sion that the cause of the adaptive modification of flowers 

 must be sought for elsewhere. 



At any one period the area of knowledge is always 

 bounded by a wall too high to see over, and against 

 which it is easy but not profitable to bruise one's 

 head. It is difficult to say whether it requires more 

 genius to scale the wall at one dash or to pass out by the 

 doors which are everywhere provided for those with eyes 

 to see them. And though no one would have the rash- 

 ness to suggest that there was anything defective in Mr. 

 Darwin's scientific vision, yet there is some comfort to 

 be derived from the fact that he gives from his own 

 experience a most instructive instance of the real diffi- 

 culty that even the greatest of investigators may feel in 

 emancipating himself from the limits which preposses- 

 sion — conscious or unconscious — constantly opposes to 

 Vol. XV.— No. 381 



the progress of research. Without, of course, having a 

 shadow of doubt that nature had some need to satisfy in 

 so laboriously struggling to prevent self-fertilisation in 

 plants, Mr. Darwin was content to suppose that it might 

 be injurious in the long run, in some way difficult, at 

 present — if ever — to be analysed, and, to use his own 

 words : — 



" That it would be necessary, at the sacrifice of too much 

 time, to self- fertilise and intercross plants during several 

 successive generations in order to arrive at any result. 

 I ought [he continues] to have reflected that such elabo- 

 rate provisions favouring cross-fertilisation, as we see in 

 innumerable plants, would not have been acquired for the 

 sake of gaining a distant and slight advantage, or of 

 avoiding a distant and slight evil " (p. 8). 



In fact an observation almost accidental led the way 

 to the remarkable discoveries recorded in the present 

 volume. Of these an article in the Academy (August 

 28, 1875) by Mr. George Darwin gave, I believe, the 

 first intimation, and raised in the highest degree our ex- 

 pectations. "My father," he stated, "has now been 

 carrying on experiments for about nine years on 

 the crossing of plants, and his results appear to him 

 absolutely conclusive as to the advantages of cross- 

 fertilisation to plants." Mr. Darwin informs us that he 

 was led to the investigation by the manifest contrast pre- 

 sented by " two large beds of self-fertilised and crossed 

 seedlings from the same plant of Linaria -vulgaris " 

 (p. 9), in which he found to his surprise that " the crossed 

 plants when fully grown were plainly taller and more 

 vigorous than the self-fertilised ones." His "attention 

 was now thoroughly aroused," and two-thirds of the pre- 

 sent volume are devoted to the very extended course of 

 experimentation, the results of which Mr. Darwin puts 

 forward in confirmation of the conclusion which his first 

 and accidental observation suggested. These results 

 deserve and will receive the most careful study at the 

 hands of botanists, but it would be scarcely useful within 

 the limits of this notice to examine them in any detail. 

 They appear, however, to me, to demonstrate completely 

 the advantage which cross-fertilised plants obtain in all 

 that concerns their struggle for life — in increase of size, 

 of bulk (as measured by weight), and of fertility, as well 

 as in precocity of flowering and capacity of resisting 

 adverse external influences. 



The remainder of the volume is, however, occupied 

 with general discussions, upon which it may be interest- 

 ing to make some remarks. The process of gamogenesis 

 essentially consists in " the physical admixture of proto- 

 plasm derived from two sources." Mr. Darwin's investi- 

 gations have left no room for even a shadow of a doubt 

 that the object of nature in bringing about this result is to 

 secure for the starting-point of the new organism a proto- 

 plasmic mass made up of elements which have been inde- 

 pendently individualised or differentiated by exposure 

 to different external conditions. Mr. Herbert Spencer 

 explains this by the need which the manifestation of life 

 involves for continually disturbing the condition of mole- 

 cular equilibrium to which all things in nature gradually 

 tend. But as Mr. Darwin hints, this mode of explanation 

 scarcely does rhore than restate the empirical facts which 

 we may now sum up by saying that for gamogenesis to 

 give the best result a certain mean differentiation — vary- 



