DESERT SANDS 351 



long periods together ; and the camel, the most inveterate 

 desert-haunter of the trio, is even provided with a special 

 stomach to take in water for several days at a stretch, 

 besides having a peculiarly tough skin in which perspiration 

 is reduced to a minimum. He carries his own water-supply 

 internally, and wastes as little of it by the way as possible. 



What the camel is among animals that is the cactus 

 among plants the most confirmed and specialised of 

 desert-haunting organisms. It has been wholly developed 

 in, by, and for the desert. I don't mean merely to say that 

 cactuses resemble camels because they are clumsy, ungainly, 

 awkward, and paradoxical ; that would be a point of view 

 almost as far beneath the dignity of science (which in spite 

 of occasional lapses into the sin of levity I endeavour as a 

 rule piously to uphold) as the old and fallacious reason 

 ' because there's a B in both.' But cactuses, like camels, 

 take in their water supply whenever they can get it, and 

 never waste any of it on the way by needless evaporation. 

 As they form the perfect central type of desert vegetation, 

 and are also familiar plants to everyone, they may be taken 

 as a good illustrative example of the effect that desert con- 

 ditions inevitably produce upon vegetable evolution. 



Quaint, shapeless, succulent, jointed, the cactuses look 

 at first sight as if they were all leaves, and had no stem or 

 trunk worth mentioning. Of course, therefore, the exact 

 opposite is really the case ; for, as a late lamented poet hag 

 assured us in mournful numbers, things (generally speak- 

 ing) are not what they seem. The true truth about the 

 cactuses runs just the other way ; they are all stem and no 

 leaves ; what look like leaves being really joints of the trunk 

 or branches, and the foliage being all dwarfed and stunted 

 into the prickly hairs that dot and encumber the surface. 

 All plants of very arid soils for example, our common 

 English stonecrops tend to be thick, jointed, and succu- 



