CH. Il] 



POTATO. 



25 



At present it may be taken for granted that the tuber 

 of the potato is a stem. It is a stem in which growth in 



T 

 Fm. 8. 



SEEDLING POTATO-PLANT BEARING TUBERS. 

 L, leaves. <7, cotyledons. TT, tubers. 



R, root. 



thickness has been excessive, as may be seen by comparing 

 the tuber with the stalk which bore it. The biological 

 meaning of the tuber is illustrated by the use to which 

 gardeners put it in the culture of the plant; instead of 

 sowing the seed of the potato they cut up the tuber into 

 bits, and plant these ; they take advantage, in fact, of the 

 part which the tuber is destined to play in the natural 

 course of the plant's life, namely, to provide for the con- 

 tinuance of the species. 



It is a bit of everyday knowledge that the gardener 

 cutting up a potato for "seed" takes care that each bit 



