THE ST A PELF A FAMILY. i8i 



the tip describes a wide circle, and so comes in contact 

 with some plant. By continning " to bow around," it 

 twists itself spirally round the support. 



Several genera of this family, as well as of another 

 to be described hereafter {EwpliorhiacecE), are specially 

 adapted to live in the dry climate of South and West 

 Africa, by having acquired a thick, fleshy stem, in 

 which much gummy or milky fluid is stored up. The 

 surface forms a tough, rind-like covering which prevents 

 the loss of water by transpiration. 



As the climate of Mexico is of a similar nature, 

 plants of a quite different family, Cactacecc, put on a 

 similar external appearance. Thus, stems of some 

 members of this family are just like those of Stapelia 

 (Fig. 75, I.), as also of EuT)liorUa, being thick, many- 

 angled, fleshy, and leafless, the leaves being replaced 

 by spines. 



The fact is that this peculiar form of stem of both 

 Cac'tus and Stape'lia and others, is the actual result of 

 living under similarly arid conditions of the localities 

 where fchey grow. The plants resjjond to the external 

 influences ; and in the course of several generations 

 form the remarkable structures which become a 

 permanently fixed feature. 



Stapelia (Fig. 75). — The flowers of all members 

 of this order are somewhat difficult to understand ; but 

 the beginner must look for the following details 

 carefully : — 



