STEMS 



59 



Caladium, this stem-like character is less evident. The 

 potato is an excellent example of the short and much- 

 thickened underground stem known as a tuber. 



It may be seen from Fig. 33 that the potatoes are none 

 of them borne on true roots, 

 but only on subterranean 

 branches, which are stouter 

 and more cylindrical than 

 most of the roots. The 

 " eyes " which they bear are 

 rudimentary leaves and 

 buds. 



Bulbs, whether coated like 

 those of the onion or the 

 hyacinth (Fig. 34), or scaly 

 like those of the lily, ai'e 

 merely very short and stout 

 underground stems, covered 

 with closely crowded scales 

 or layers which represent 

 leaves or the bases of leaves 

 (Fig. 35). 



The variously modified 

 forms of underground stems 

 just discussed illustrate in a 

 marked way the storage of 

 nourishment during the 

 winter (or the rainless sea- 

 son, as the case may be) to secure rapid growth during 

 the active season. It is interesting to notice that nearly 

 all of the early flowering herbs in temperate climates, like 

 the crocus, the snowdrop, the spring-beauty, the tuUp, and 



Fig. 32. Roots, Rootstocks, 

 and Leaves of Iris. 



