CACTUS, OR PRICKLY-PEAR TRIBE. 443 



form the functions of leaves. In the various species of Cactus, 

 however, we find the form of the stem differing greatly. Thus 

 in one kind, known as the Melon-Cactus from its form, the stem 

 is so much stunted as well as expanded, that it quite resemble? 

 the fruit alluded to. In other species, however, the stems are 

 round and greatly prolonged, resemblin^ ropes ; whilst in others, 

 again, they are equally long, but are angular. All are adapted 

 to the same circumstances of growth ; but the Melon-Cactus, 

 from its greater bulk, in proportion to the surface it presents, 

 can exist in the most exposed situations. It usually happens in 

 tropical climates, that, during a certain portion of the year, a 

 large quantity of rain falls, the atmosphere is loaded with damp- 

 ness for many weeks, and the soil is completely saturated with 

 water. During this time, the Cactuses live very fast, and dis- 

 tend all the cavities of their tissue with fluid. The resistance 

 afforded by their thick cuticle, and by the deficiency of stomata, 

 to the evaporation of this, enables them to retain a store of it 

 (as the Camel holds water in the stomach) until they can ac- 

 quire a fresh supply. At other times, they may be said to live 

 very slowly; the functions of exhalation, digestion, &c., are 

 performed very inactively ; and the fluid which they have ab- 

 sorbed during the rainy season is adequate for their support, 

 during all those months when they cannot live upon the soil or the 

 atmosphere. This property sometimes renders the Cactus tribe 

 of great utility to man. On Mount Etna, for example, and itf, 

 volcanic fields, it is the Indian "Fig which the Sicilians employ, 

 to render such desolate regions susceptible of cultivation. This 

 plant readily strikes into the fissures of the lava, and soon, by 

 extending the ramifications of its roots into every crevice of the 

 stone, and bursting the largest blocks asunder by their gradual 

 increase, makes it capable of being worked. The juiciness of 

 the stems causes them to be sought in the West Indies, during 

 dry seasons, by the cattle; which, tearing off the thorny integu- 

 ment that covers them, feed upon the moist pulp within. 



611. The flowers of this tribe are commonly very showy ; 

 and the number of handsome species, which have been of late 

 introduced into our hothouses, gives them an air of splendour 



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