74 The Great World*s Farm 



mizing their foliage, and give up having any true leaves 

 at all as soon as they are full-grown. They keep their 

 leaf-stalks indeed, but there are no leaves at the end of 

 them, and instead there are ** wings," or narrow, leaf-like 

 margins, growing out from each side of the stalks. Even 

 these "wings" do not venture to face the sun, but turn 

 their edges to earth and sky. 



Acacias are especially the trees of deserts; they are, 

 indeed, the only timber-trees of the Arabian Desert, and 

 they abound in Africa, as also in Australia. But wherever 

 they grow they are characterized by the lightness of their 

 foliage; and of the Australian species, which number 

 something under three hundred, two hundred and seventy 

 drop their leaves altogether when they are grown up, and 

 merely flatten out their leaf-stalks as described. 



None of the cactus family — which are natives of the 

 hot, dry regions of America, North, South, and Central — 

 make any attempt at having leaves or even "wings," but 

 their stems are flattened out and do duty instead. The 

 stems, too, are protected against evaporation by being 

 enveloped in a peculiar leathery skin, which is thickest in the 

 species inhabiting the hottest and driest regions; and they 

 lose little water therefore, except through the pores, which 

 are but few in number. Thus protected, they not only 

 exist, but flourish, in dry sand, where for three-quarters 

 of the year they are exposed to the blazing, parching sun. 



The tall, fluted columns of the species of cactus called 

 the "torch thistle," sometimes fifty feet high, are to be 

 seen springing out of crevices in the hard rock, and stand- 

 ing up like telegraph-posts on the mountains and in the 

 rocky valleys all over the hot, parched, almost desert 

 regions of New Mexico. 





