60 



THE STEM 



are at once seen to be different from the roots, both in appearance 

 and manner of growth. The scales on the tubers are the rudiments 

 of leaves ; the eyes are the buds in their axils. The Potato plant 

 rears annual stems that bear ordinary leaves expanded in the air, to 

 digest what they gather from it and what the roots gather from the 

 soil, and convert these substances into nourishment. A large part of 

 this nourishment, while in a liquid state, is carried down the stem, into 

 the underground branches, and accumulated in the form of starch at 

 their extremities, which become tubers, or depositories of prepared solid 

 food, — just as in the Turnip, Carrot, and Anemonella (Figs. 35, 36), 

 it is deposited in the root. Taking advantage of this, man has trans- 

 ported the Potato from the cool Andes of Chile to other cool climates, 

 and made it yield him a copious supply of food, especially important 

 in countries where the season is too short, or the summer's heat too 

 little, for profitable cultivation of the principal grain plants. 



49. Cyclamen. 



50. Indian Turnip {Arissenia) . 



95. The corm or solid bulb, like that of Cyclamen (Fig. 49), and 

 of Indian Turnip or Jack-in-the-pulpit (Fig. 50), is a very short and 

 thick fleshy subterranean stem, often broader than high. 



96. The bulb, strictly so-called, is a stem like a reduced corm as to 

 its solid part (or plate) ; while the main body consists of thickened 



scales, which are leaves or leaf 

 bases. These are like bud 

 scales ; so that in fact a bulb is 

 a bud with fleshy scales on an 

 exceedingly short stem. Com- 

 pare a White Lily bulb (Fig. 51) 

 with the strong scaly buds of 

 the Hickory (Fig. 17), and the 

 resemblance will appear. In 

 corms, as in tubers and root- 

 stocks, the store of food for 

 future growth is deposited in the 

 stem; while in the bulb, the 

 greater part is deposited in the bases of the leaves, changing them 

 into thick scales, which closely overlap or inclose one another. 



51. Bulb of White Lily. The longitudi- 

 nal section shows two buds of 

 the next year. 



