Makch 15, 1895.] 



SCIENCE. 



283 



of plants was not original with Gaudichaud, 

 but he greatly enlarged it and gave it most 

 of its historic value, and, what is more to 

 our purpose, he used the word phyton, 

 which, in lieu of a better one. I shall use as 

 a convenient expression for that asexual 

 portion of any plant which is capable of re- 

 producing itself. Gaudichaud's fanciful 

 hypothesis was not completely overthrown 

 until the exact studies of Von Mohl upon 

 the vegetable cell established a rational 

 basis of morphology and physiolog}'. 



What I Avish now to show is that the 

 evolution of the vegetable kingdom cannot 

 be properly understood until we come to 

 feel that the phyton, or each portion of the 

 plant, which, when removed, has the capa- 

 bilitj- of reproducing itself and its parent, 

 is in reality a potential autonomy. In 

 doing this I shall not forget that the plant 

 also has an individuality as a whole, but as 

 this feature is quite aside fi-om my argu- 

 ment and is the conception of the plant 

 which is every^vhere accepted, I shall, ne- 

 cessarily confine my remarks to the indi- 

 vidual life of the phyton. The mere fact 

 that the phjiion may reproduce itself is not 

 the most important point, but, rather, that 

 each part of the plant maj' respond in a 

 diflferent manner or degree to the effects of 

 environment and heredity. Before proceed- 

 ing to this matter, I should say that there 

 is no doubt about the capability of every 

 plant to lie propagated asexually. It is 

 true that all plants have not been so propa- 

 gated, but there is every reason to suppose 

 that the gardener can acquire the requisite 

 skill to grow, oaks and hickories from cut- 

 tings were it worth his while to do so. At 

 present there are cheaper modes of multi- 

 plying these plants. But certain pines and 

 spruces, which do not seed under cultiva- 

 tion, are propagated by cuttings, and the 

 tissue of the.se trees is as little adapted to 

 such use as that of any plants with which I 

 am acquainted. The fact that plants are 



not grown from cuttings does not prove 

 that they cannot be so propagated, for we 

 know that the essential structure of all of 

 them is very similar, and that each node 

 and internode — or each phyton- — does or 

 may produce branches and flowers and 

 seeds when it is borne upon its parent plant. 

 And I should remind you that those plants 

 which are not readily multiplied by cuttings 

 are generally propagated by grafting, which, 

 for illustration, amounts to the same thing, 

 for we only substitute the stock of another 

 plant for the soil. Plants of the most vari- 

 ous kinds are readily multiplied by graft- 

 age. Even tuberous herbaceous stems, 

 which are not commonly associated with 

 the arti of the grafter, unite with ease. One 

 of the latest investigators in this field is a 

 Frenchman, Daniel, and his conclusions 

 upon the physiology of gi'afted plants show 

 that the phj-siological modifications in these 

 plants are largely such as arise from physi- 

 cal causes, showing that the parts still 

 preserve their essential autonomy. 



Now, if every plant varies in the number 

 of parts, or phytons, of which it is com- 

 posed, it follow'S that this number must be 

 determined by agencies which act imme- 

 diately upon the given plant itself. AVe all 

 know that the number of these parts is de- 

 termined veiy largely by environment. 

 A dozen plants springing from the same 

 capsule may vary immensely in the num- 

 bers of their branches, leaves and flowers, 

 and this variation is generally obviously 

 correlated with amoimt of food, amount of 

 space which the plant is allowed to occupy, 

 and other physical conditions which afl'ect 

 its welfare. But we not only find that no 

 two plants have the same number of parts, 

 but that no two branches in the same plant 

 are alike. One part grows longer, one more 

 erect, one has greener leaves, one bears 

 more fruit. So, too, there may be different 

 forms of flowei*8 on the same plant, a sub- 

 ject to which Darwin has devoted an entire 



