352 DESEET SANDS 



lent ; the distinction between stem and leaves tends to dis- 

 appear ; and the whole weed, accustomed at times to long 

 drought, acquires the habit of drinking in water greedily 

 at its rootlets after every rain, and storing it away for future 

 use in its thick, sponge-like, and water-tight tissues. To 

 prevent undue evaporation, the surface also is covered with 

 a thick, shiny skin a sort of vegetable macintosh, which 

 effectually checks all unnecessary transpiration. Of this 

 desert type, then, the cactus is the furthest possible term. 

 It has no flat leaves with expanded blades, to wither and 

 die in the scorching desert air ; but in their stead the thick 

 and jointed stems do the same work absorb carbon from 

 the carbonic acid of the air, and store up water in the driest 

 of seasons. Then, to repel the attacks of herbivores, who 

 would gladly get at the juicy morsel if they could, the 

 foliage has been turned into sharp defensive spines and 

 prickles. The cactus is tenacious of life to a wonderful 

 degree ; and for reproduction it trusts not merely to its 

 brilliant flowers, fertilised for the most part by desert moths 

 or butterflies, and to its juicy fruit, of which the common 

 prickly pear is a familiar instance, but it has the special 

 property of springing afresh from any stray bit or fragment 

 of the stem that happens to fall upon the dry ground any- 

 where. 



True cactuses (in the native state) are confined to 

 America ; but the unhappy naturalist who ventures to say 

 so in mixed society is sure to get sat upon (without due 

 cause) by numberless people who have seen ' the cactus ' 

 wild all the world over. For one thing, the prickly pear 

 and a few other common American species, have been 

 naturalised and run wild throughout North Africa, the 

 Mediterranean shores, and a great part of India, Arabia, 

 and Persia. But what is more interesting and more confus- 

 ing still, other desert plants which are not cactuses, living in 



