STEMS AND BRANCHES AND THEIR USES 201 



Fig. 122. — 4, a lily bulb. S, the bulb 

 of a hyacinth cut lengthwise through the 

 middle. A after Gray. 



(Fig. 121). But in some plants certain parts of the stem or 



of the branches are set apart as storage organs, and several of 



the special stem struc- 

 tures that we have to 



consider are organs of 



this kind. Others are 



supporting organs, and 



still others serve as 



means of multiplication. 

 220. Bulbs and Corms. 



— A bulb consists of a 



short stem covered by 



fleshy leaves ; the leaves 



contain most of the 



plant's reserve food. 



Some bulbs, like those 



of the onion, tulip, and hyacinth (Fig. 122, B), have leaves 



so large that the outer ones completely cover the inner 



leaves. Others, including the bulbs of lilies (Fig. 122, A), 

 have smaller leaves that merely over- 

 lap one another like the scales of a 

 fish. " Multiplier " onions produce 

 many branch bulbs in the axils of 

 their bulb leaves. The crocus has 

 a globular underground stem that 

 sends up a flower-bearing shoot in 

 the spring just as the onion bulb 



Gladiolus does. But this bulb-like body of 



Last year's corm, ,. . j 1 u ii,- 



now dead and decaying, is ^^^ ^rocus IS covered only by thi;i 



in the center. On either scales ; nearly its whole thickness is 



side is a branch corm which made up of the stem, and most of 



is sending up a flowering ^j^^ ^^^^^ ^^^^ .^ ^^^^^^ -^ ^^^ 

 shoot this year, 



stem instead of in the leaves. A 



body like this is a corm. The jack-in-the-pulpit (Indian 

 turnip) and the gladiolus (Fig. 123) also have corms. 



