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favorite localities, and there, amidst surrounding aridity, they elaborate 

 that pleasantly flavored acid juice so refreshing to the traveller, and 

 which even the wild ass knows instinctively how to avail himself of, 

 by stripping off the spines of the Melocactus with his hoof, and then 

 sucking the cooling lymph from the fleshy tissue. The peculiar 

 habit of the plants belonging to this order has given rise to some 

 plausible but unfounded opinions connected with them, which are 

 well exposed in the next extract. 



"The Cactaceae have long been compelled, in science, to serve as 

 the prop of a statement which, altogether false, has yet been frequently 

 put forward by distinguished botanists ; I mean, the assumption that 

 many, or even all plants are capable of imbibing their nutriment from 

 the air. Even in the present day has this idea been again revived, 

 with all the long-ago-refuted reasons, by Liebig, whose ' Organic 

 Chemistry ' has made so imposing an appearance. It is believed, 

 that from the vast amount of watery juice in the Cactus tribe, joined 

 to the fact that most of them, and exactly those richest in sap, vege- 

 tate on dry sand, almost wholly devoid of vegetable mould, where 

 they are besides exposed, often three-fourths of the year, to the parch- 

 ing sunbeams of an eternally serene sky ; from this combination of 

 circumstances, even, it is thought that we may the more safely con- 

 clude, that these plants draw their nourishment from the air, since in 

 our own hot-houses also it has been observed, that the branches of 

 Cactus stems, cut off and left forgotten in a corner without further 

 care, far from dying, have frequently grown on and made shoots three 

 feet long or more. De Candolle first found the right path, when he 

 weighed such Cactus shoots which had grown without soil, and found 

 that the plant, though larger, was always lighter ; therefore, instead 

 of abstracting anything from the atmosphere, must rather have given 

 up something to it. All the growth takes place, in such cases, at the 

 expense of the nutritive matter previously accumulated in the juicy 

 tissue, and it generally exhausts the plant to such a degree, that it is 

 no longer worth preserving. It is that succulent tissue which enables 

 the Cactus plants, — one might compare them with the camels, — to 

 provide themselves before-hand with fluid, and thus to brave the rain- 

 less season. Their anatomical structure also assists them in this re- 

 spect, in a peculiar manner. We know, from the experiments of 

 Hales, that plants chiefly evaporate the water they contain through 

 their leaves, and the Cactus tribe have none. Their stem, too, unlike 

 that of all other plants, is clothed with a peculiar leathery membrane, 

 which wholly prevents evaporation. This membrane is composed of 



