STEMS AND BRANCHES AND THEIR USES 2OI 



(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 FIG. I22 .-J,a lily bulb. B, the bulb 

 of a hyacinth cut lengthwise through the 

 plant's reserve food, middle. A after Gray. 

 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 

 FIG. 123. Gladiolus does. But this bulb-like body of 

 corms. Last year's corm, , . . , , , , . 



now dead and decaying, is the crocus 1S covered only by thtfi 

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

 side is a branch corm which ma d e up o f t h e stenij an( J most o f 

 is sending up a flowering ,, / j j j.1 



shoot this year e reserve food is stored in the 



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. 



