178 ABSORPTION OP FLUID BY THE LEAVES. 



studded here and there with plants of the Cactus and Orchis 

 tribes ; the former exciting attention by the brilliancy of their 

 blossoms, and the latter by the strange shapes they often pre- 

 sent. In many of the Cacti growing in such situations, the 

 stems contain a considerable amount of fluid ; which, though 

 insipid, is wholesome, and is freely used as a cooling drink in 

 fevers, by the natives of the countries in which these plants 

 abound. 



272. Many of the Orchis tribe (as well as other plants) grow 

 entirely in the air ; spreading themselves over the surface of 

 trees, from which their roots hang freely down like fringes. Such 

 attain their greatest luxuriance, in the forests of the tropical 

 parts of South America ; and here a constantly moist state of the 

 atmosphere is maintained, by the exhalation of the trees, upon 

 which they cluster. When grown in hot-houses in this country, 



Fro. 73. AERIDES ARACHNOIDES. 



they require that the atmosphere should be rendered artificially 

 moist, as well as warm ; and that their roots should be enabled 

 to spread themselves freely through the air, and should not be 



