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TEXTBOOK OF BOTANY 



and flat and look exactly 

 like leaves ; one can tell 

 that they are branches only 

 by noticing that each one 

 grows from the axil of a 

 scale-like leaf. 



The thick green stems of 

 the members of the cactus 

 family and of some other 

 plants living in very dry- 

 regions take on remarkable 

 shapes. The leaves and 

 most of the branches of 

 nearly all cactuses are re- 

 duced to scales or spines. 

 The advantage of such an 

 arrangement will appear in 

 connection with our study 

 of leaves. The stems of 

 cactuses not only manufacture and store food ; they are 

 organs for water storage as well, and are often an important 

 source of water for travelers in the desert where these plants 

 grow. The stem of 

 the ' ' nail-keg cactus ' ' 

 is said to yield some- 

 times as much as a 

 pint of water. 



223. Runners. — 

 This name is given 

 to certain branches 

 (of the strawberry, 

 for example) which 



sprawl on the surface 



f ,■, A u ^^^' — ^ "strawberry geranium 



01 the ground, nave {Saxifraga sarmcnlosa), which bears runners 



long internodes, and much like those of a strawberry. 



Fig. 126. — A cactus (Opiinlia), 

 whose stem is thick and green, and 

 whose leaves are merely spines. 



