84 THE SURVIVAL OF THE UNLIKE. [ill. 



phyton. He proposed that the leaf, with its connecting 

 tissues, is the vegetable individual, and that the plant is 

 a colony of these individuals. Gaudichaud offered this 

 theory as an explanation of the morphology and physi- 

 ology of plants, and the hypothesis really has no place 

 in the present discussion; but, inasmuch as I have bor- 

 rowed 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, incidentally, to illus- 

 trate some of the problems of individuality to which I 

 shall recur. Gaudichaud, while recognizing that a cell 

 which develops into a bud is itself an individual, never- 

 theless considered that the leaf, with its dependent tis- 

 sues, represents the simple vegetable unit. Each of 

 these units has an aerial or ascending part and a radicu - 

 lar part. The ascending part has three kinds of tissues 

 or merithals — the stem merithal, the petiolar merithal and 

 the limbic merithal. Now, each phyton fixes itself upon 

 the trunk, or upon an inferior phyton, in the same man- 

 ner 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 extension of these threads 

 produces the thickening of the stem, and the superposi- 

 tion of phytons increases the height of the plant. This 

 mechanical theory of the morphology 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 

 reproducing itself. Gaudichaud's fanciful hypothesis 

 was not completely overthrown until the exact studies 



