Ch. IV, 11] SPECIAL FUNCTIONS OF STEMS 



193 



single spine of the Cactus-like Euphorbias is a stem, really 



the persistent and hardened flower-bearing branch. As in 



case of leaves, however, 



the significance of these 



spines is uncertain (page 



79). 



Support of the flowers, 

 which mostly stand out 

 in the light, is another of 

 the special functions of 

 stems. Flower stalks 

 are usually slender-cylin- 

 drical, nodeless, and leaf- 

 less, though sometimes 

 they bear bracts (page 

 73). An elongated stem 

 ending in a single flower 

 or small cluster, espe- 

 cially if starting directly 

 from the ground, as with Adder' s-tongue or Violets, is called 

 a scape ; a flower stalk from the axil of a leaf is called a 



peduncle, and in clusters 

 each separate stalk is a 

 pedicel. A typical flower 

 stalk consists really of one 

 internode, bearing at its 

 top several nodes merged 

 together in one enlarged 



RECEPTACLE which SUp- 



ports the floral parts (page 

 271). 



The most striking of the 

 new functions assumed by 

 stems is found in the re- 

 placement of leaves as 

 foliage. In the simplest 



Fig. 137. — Spine, a branch 

 developed from an axillary bud, 

 in Honey Locust ; X \. 



Pio. 138. Rvbut auitrali*, a shrub 

 in which the foliage function is assumed 

 by the stem and petioles; much reduced. 

 (From Wiesner.) 



