245 



'Vegetable Kingdom.' As Schleiden well observes, "Everything 

 about these plants is wonderful ;" even their internal structure differs 

 widely from that of all other members of the exogenous class, and in 

 the absence of leaves (which organs are replaced by hairs and spines), 

 in the peculiar structure of their epidermis, and in the extraordinary 

 quantity of oxalic acid secreted (forming insoluble crystals of oxalate 

 of lime with the proportionate quantity of that earth taken up into the 

 system), the Cactaceae offer some of the most curious phenomena to 

 be found in the whole vegetable race. 



" With the exception of the genus Pereskia, no plant of the order 

 possesses leaves. Those parts of the Cactus alatus, and the Indian 

 fig, which are commonly called leaves, are nothing but flattened ex- 

 pansions of the stem. On the other hand, they are all distinguished 

 by an extraordinary fleshy stem, which, clothed by a grayish-green, 

 leathery cuticle, and beset, in the places where leaves are situated in 

 regular plants, with various tufts of hairs, spines, and points, gives, by 

 its very varied degrees of development, the varied character of the 

 plants. The torch-thistles rise in form of nine-angled or often round 

 columns, to a height of thirty or forty feet, mostly branchless, but 

 sometimes ramifying in the strangest ways, and looking like candelabra; 

 the Indian figs are more humble ; their oval, flat branches, arranged 

 upon one another on all sides, produce special forms. The lowest and 

 thickest torch-thistles connect themselves with hedgehog and melon 

 Cactuses, with their projecting ribs, and thus lead us to the almost per- 

 fectly globular Mammillarias, which are covered very regularly with 

 fleshy warts of various heights. Finally, there are forms in which the 

 growth in the longitudinal direction prevails, which, with long, thin, 

 often whip-like stems, like that of the serpent Cactus, so often culti- 

 vated here, hang down from the trees upon which they live as para- 

 sites."— p. 215. 



Linnaeus seems to have known only about a dozen species of this 

 family, which were all grouped together in his genus Cactus : Schlei- 

 den states the number now known at more than four hundred, distri- 

 buted into ten genera; and Lindley, in his 'Vegetable Kingdom,' 

 gives the number of species at eight hundred (with two marks of 

 doubt), and sixteen genera. America is the exclusive station of the 

 order, no other part of the globe appearing to possess a legitimate 

 claim to a single indigenous species, though many have rapidly 

 become naturalized in Europe and other parts of the Old World, 

 since their introduction from America. The driest situations, where 

 they are exposed to the burning rays of the tropical sun, are their 

 Vol. in. 2 l 



