1892.] MICEOSCOPICAL JOUENAL. 100 



cells in the embryonic part of the bud requires food, to furnish 

 which is the reason for the starch supply. But after a time the 

 growing bud-tissue differentiates into stem and leaves and rootlets, 

 and then it can begin to depend, as all green plants do, upon the 

 sunlight aiKl the water and gases of the air and soil, and with 

 their help to construct its own substance. The starch of the po- 

 tato tuber thus acquires a biological meaning. Its production 

 and storage are perfectly analogous to the provision made in seeds. 

 I have alreadv referred to the case of the peanut, where we have 

 also an undergroimd structure stored abundantly with food for 

 the undeveloped embryonic tissue, which is also part of the nut. 

 The substance in many seeds is largely albuminous, as shown so 

 abundantly in the pea and bean, also in the peanut, which is a 

 close ally of the pea and bean. 



Since the potato tuber and the pea or bean are thus comparable 

 in two respects, both being the starting-point of new individual 

 plants and both containing cells which secrete and amass large 

 quantities of food to nourish the embryo .plant until its vegetative 

 organs are developed, a hasty conclusion might be made by some 

 that the potato is a sort of seed. This conclusion would be 

 found by the study of the anatomy of the entire plant to be true 

 only in a very particular sense, and not as meant in ordinary 

 terms. The seed is the product of a ripened flower, while the 

 tuber is not. There is a very great difference in the powers of 

 potato-seed and of the tuber-bud ; the latter propagates its kind 

 absolutely and without variation, while propagation from seeds is 

 very likely to result in the appearance of varieties unlike the par- 

 ent plant. We have in this case an example of the law that 

 nature works very variously toward the same end, using the stem- 

 , bud in one case as the special organ of propagation and the seed 

 in another, equipping either suitably for its purpose. 



Finallv, if we compare the potato with an animal, we find that 

 the aggregate of its actions are anabolic, that is, they are con- 

 structive, so that as their result elements, or simple inorganic 

 compounds, are laid hold upon and caused to combine to form 

 higher and more complex organic compounds used in the plant's 

 structure. In this it is unlike an animal, the aggregate of whose 

 activities is katabolic, for it takes in highly complex chemicals 

 (furnished from the plant's work) and gives out simpler ones. 

 Associated with the difference is the further fact that the func- 

 tions of motility and sensation, which are so characteristic of ani- 

 mals and are possible by reason of the constant katabolic charac- 

 ter of its metabolisms, are unspecialized in the plant if not entirely 

 absent, while the metabolic function is highly specialized and re- 

 sults in the production of anabolic products in the vast amount 

 we see in the tuber. 



We see then that the same forces are at work in the vegetable 

 as in the animal body. The active agents of the tuber are pro- 

 toplasmic cells, which work along lines determined by inheritance, 



