322 



Introduction to Botany. 



readily, and containing but a moderate amount of soluble 

 salts. 



207. Character of Xerophytes. — Since the xerophytes 

 have developed under conditions requiring a reduction of 

 transpiration and the appropriation of as much as possible 

 of the scant water supply, we find that they are character- 

 ized by (i) a reduction of leaf and stem surfaces without a 

 corresponding reduction in volume, — that is, while the stems 

 and leaves are less branched and expanded, they are more 



Fig. 170. 

 Zygophyllum cornutmn from the Algerian desert. After Engler. 



fleshy, as in Cactus, Portulacca, and Mesembryanthemum 

 (Fig. 169); (2) a reduction of intercellular spaces so that 

 more room may be obtained for the storage of water, 

 the transpiring surfaces being reduced at the same time ; 

 (3) increase- in tissues which absorb, conduct, and store 

 water; (4) frequently a covering of hairs, scales, etc., 

 which reduce transpiration ; (5) a lengthening of the pali- 

 sade cells ; (6) depression of the stomata beneath the sur- 

 face, and (7) the production of mucilage which assists in 

 retaining the water within the plant. 



