TYPES AND KINDS OF STEMS 51 



the potato tuber is formed. Some of the starch that is made in 

 the leaves during the day is transported to these underground 

 shoots and stored up in the tuber. 



82. Propagation of the potato. The potato plant is prop- 

 agated by planting the tubers, or pieces of them containing the 

 eyes. The new potatoes are borne at the end of the horizontal un- 

 derground stems which are colorless and have scale-like leaves. 



83. Experiments with the potato plant. Tubers kept in a 

 warm room during the winter often " sprout," the sprouts or 



Fig. 49. 



Desert vegetation, Arizona, showing large succulent trunks of cactus with shrubs and 

 stunted trees. Open formation. (Photograph by Tuomey.) 



shoots developing from the eyes. Sometimes when kept in a box 

 or drawer, even in the absence of light, they will form colorless 

 shoots and a new crop of small potatoes. If placed in a vessel in 

 contact with a little water, and kept in a warm room in strong 

 light, green shoots and leaves will develop.* If the growing 



*See "Water Culture Method for Experimenting with Potatoes," Plant 

 World, n, 249-254, 1908. 



