THE STEM 



243 



Fig. 220.— Spine of 

 Flacourlia sepiaria. 



Fig. 221. 

 Root-stock of Water-Lily 



In Flacourtia sepiaria, Randia, Canthium, Carissa and a 

 number of similar shrubs found in the jungles, axillary branches 



are modified into thorns or spines, and form a 

 means of protection from damage by herbivo- 

 rous animals. 



In the Passion-flower branches are changed 

 into tendrils for climbing. The tendrils of 

 the vine are the ends 

 of the main shoots 

 (see p. 241), those 

 of Antigonon are the 

 stalks of the inflores- 

 cence. 



By means of itn- 

 derground shoots per- 

 ennial herbs are enabled to live during the adverse season. 

 The three chief types of such stems are: — 



(a) the Root-stock or Rhizome (Canna, Ginger), 



(b) the Bulb (Onion), 



(c) the Tuber (Potato). 



The Root-stock or Rhizome (see Water-lily, p. 4; Ginger, 

 p. 164) is either a short vertical stock with 

 a crowded leaf-rosette as in Elephantopus, 

 or a horizontally creeping stem of nionopo- 



dial growth 



as in most 



F e r n s, o r 



one of 



sympodial 



growth as 



in Canna. 



E X a m i n e, 



for instance 



the creep- 

 ing rhizome 



of Canna and notice the brown scarious scales covering it, thick 

 adventitious roots growing from its lower part and breaking 



16* 



Fig. 222.— Rhizome of Ginger. 



Fig. 223. — Bulb of Onion. 



