5i6 THE STRUCTURE OF ECONOMIC PLANTS 



than the central part of the lamina. Stomata are more numerous 

 on the abaxial surface. 



The leaves that develop on the subterranean portions of the 

 stem are small and scale-like. Buds formed in the axils of these 

 leaves produce rhizomes which elongate rapidly and develop tubers 



Fig. 2.71. Face and side view of potato seed and stages in development of seedling. 



at their extremities. According to Clark (7), the rhizomes are 

 variable in length, ranging from less than an inch to 18 inches, 

 but they do not usually exceed 3 to 4 inches in cultivated varieties. 

 The tuber is morphologically a fleshy stem bearing buds or "eyes" 

 in the axils of small scale-like leaves which are soon shed, leaving 

 a ridge or leaf scar subtending the bud. 



Vegetative propagation results from the development of axillary 

 buds which produce shoots, and these then give rise to adventitious 



J 



