258 TEXTBOOK OF BOTANY 



Fig. 92. Pictures of corms of gladiolus shortly after germination; at the right 

 is a vertical section cut from the center of a corm. Photos from P. W. Zimmerman 

 and A. E. Hitchcock, Boyce Thompson Institute. 



the axillary structures of some lilies. Young bulbs which grow from 

 tlie axillary buds of the main bulb are sometimes termed bulblets. 



Failure of the internodes of the stem to elongate may also result in a 

 head, as in cabbage; or a rosette, as in dandelion, evening primrose, and 

 mullein. Ultimately elongated stems bearing leaves and flowers develop 

 from the terminal bud in the center of the rosette. 



Thorns, spines, and prickles. Thorns are small, sharp-pointed stems; 

 they may bear buds and leaves. Common examples are the thorns of 

 hawthorn and honey locust ( Fig. 93 ) . The term spine should probably 

 be used for leaf structures alone, such as the spines of barberry and the 

 stipular spines of black locust, in spite of the fact that spines and thorns 

 in common language often refer to the same structures. Pointed struc- 

 tures common on the stems of blackberry, rose, and smilax are prickles, 

 which are merely outgrowths of the epidermis and cortex. 



Climbing and twining stems. Many plants, such as grape, Virginia 

 creeper, Boston ivy, and wild cucumber, may extend vertically some- 

 times for great distances by growing on or about other plants or objects. 

 Some stems have tendrils^ which encircle the support and anchor the 

 growing vine. The Virginia creeper and Boston ivy have branching 

 tendrils the ends of which are flattened disks or holdfasts. Tiny out- 

 growths from these holdfasts penetrate the crevices of the surface on 



■^ These should not be confused with the leaf tendrils of the garden pea or the nasturtium. 



