282 



SCIENCE. 



[N. S. Vol. I. No. 11. 



ment, that Weismannism, or the Neo- 

 Darwinian philosophy, may be true for 

 some organisms, but it is wholly untenable 

 for plants. 



There is one feature of this difference be- 

 tween the animal and the plant to which I 

 wish to call your attention on this occasion. 

 It is the meaning of individuality in the 

 two. I must say, at the outset, that when 

 I speak of a plant or an animal I refer to 

 those higher forms which the layman knows 

 by these names, for it is not my purpose to 

 discuss the original causes of divergence so 

 much as those phenomena of individuahtj^' 

 which are most apparent to the general ob- 

 server. The animal may be said to have 

 complete autonomy. It has a more or less 

 definite span of life. It grows old and dies 

 withoiit having been impaired by decay, 

 and the period of death may have no imme- 

 diate relation to environment. It has a defi- 

 nite number of parts, and each part or organ 

 is differentiated and performs one function, 

 and this function serves the whole animal 

 and not the organ itself. If any part is re- 

 moved the animal is maimed and the part 

 cannot be supplied, and the severed portion 

 has no power to reproduce either itself or 

 the animal from which it came. The only 

 means by which the animal can multiply is 

 by a union of sexes. The plant, on the con- 

 trary, has no perfect or simple autonomy. 

 It has no definite or pre-determined proxi- 

 mate span of life, except in those instances 

 when it is annual or biennial, and here du- 

 ration is an evident adaptation to environ- 

 ment. The plant frequently dies as the re- 

 sult of decay. It has not a definite number 

 of parts, and each part of the plant may 

 perform a function for itself, and the part 

 may be useful to the remainder of the plant 

 or it may not. One part is like what all 

 other parts are or may be. If one portion 

 is removed the plant may not be injured; in 

 fact, the plant may be distinctly benefited. 

 And the severed portion may not only have 



the power of reproducing itself, but it may 

 even reproduce an organism like that fi-om 

 which it came. In other words, j^lants mul-~ 

 tiply both with and without sex. Poten- 

 tially, everj' node and interuode of the plant 

 is an individual, for it possesses the power, 

 when removed and properly cared for, of 

 expanding into what we call a plant, and of 

 perfecting flowers and seeds and of multiply- 

 ing its kind. 



Those of j'ou who are botanists now re- 

 call the contention of Gaudichaud concern- 

 ing the plant unit or phyton. He proposed 

 that the leaf, -with its connecting tissues, is 

 the vegetable iadividual and that the plant 

 is a colony of these individuals. Gaudi- 

 chaud offered this theory as an explanation 

 of the morphology and physiology of plants, 

 and the hypothesis really has no place in 

 the present discussion; but, inasmuch as I 

 have borrowed the word which he proposed 

 for the plant unit, it is no more than fair 

 that I should explain his use of it ; and this 

 explanation may serve, incidental^, to il- 

 lustrate some of the problems of individual- 

 ity to which I shall recur. Gaudichaud, 

 while recognizing that a cell which develops 

 into a biid is itself an individual, neverthe- 

 less considered that the leaf, with its de- 

 pendent tissues, represents the simple vege- 

 table unit. Each of these units has an 

 aerial or ascending part and a radicular 

 part. The ascending part has thi-ee kinds 

 of tissues or merithals — the stem merithal, 

 petiolar merithal and the limbic merithal. 

 N"ow, each phj^ton fixes itself upon the 

 trunk or upon an inferior phyton, in the 

 same manner as a plant fixes itself in the 

 soil, and, sending its vascular threads 

 downwards between the bark and the wood, 

 is enabled to support itself upon the plant 

 colony; and, at the same time, the exten- 

 sion of these threads produces the thicken- 

 ing of the stem, and the superposition of 

 phjiions increases the height of the plant. 

 This mechanical theorj^ of the morphologj' 



