146 THE GEOGRAPHY OF PLANTS. 



serious," as we have seen it spelt on a boat on 

 the coast.) Cereus flagelliformis, so common in 

 our green-houses and cottage- windows, is a 

 native of South America, and of the deserts of 

 Arabia. It is not, however, to be despised be- 

 cause it is common, for its flowers are very beau- 

 tiful, and are produced in profusion, while the 

 ease with which it may be trained on trellises 

 renders it a desirable ornament. The fruits of 

 several species of the cactus tribe are used as 

 edibles, and are very grateful in hot countries. 

 On Mount ./Etna they are sold in considerable 

 quantities, and some of the varieties are excel- 

 lent. The fruit of one species (Opuntia tuna) 

 is of the richest carmine hue, and its juice 

 is employed at Naples as a water colour. But 

 the most important use of this tribe is the 

 production .of cochineal, which is not strictly, 

 however, a product of the plants, but an insect 

 allied to our lady-birds, which lives and feeds on 

 several species, chiefly on Opuntia coclrinellifera 

 and 0. tuna. The cochineal cactuses are princi- 

 pally cultivated in Mexico, Brazil, and the 

 West Indies, whence we receive our chief supply 

 of cochineal. Attempts also have been made 

 to introduce them into Teneriffe and Madeira, 

 where they appear to succeed ; but it seems pro- 

 foable that cochineal can be grown with advan- 

 tage only where labour is very cheap. The 

 quantity imported into England in 1848 was 

 2,058,560 pounds. On the table-lands of 

 southern Peru, near the limit of vegetation, 

 there are seen mounds, a foot of a foot and a 



