422 CACTACEJE. 



ture numerous spiral cells are met with, and in many cases the fibre in 

 these cells is interrupted so as to present thickened rings united by 

 membrane. These rings, when the cells are macerated, can be ob- 

 tained in a free state. Many of the plants in this order show a remark- 

 able tendency to spiral development. The seta?, spines, and hairs, are 

 sometimes arranged spirally, and in Cereus flagelliformis the cells of the 

 setae have this tendency. Many of them yield an edible fruit, which 

 is sometimes refreshing and agreeable, at other times insipid. The 

 fruit of Pereskia aculeata, under the name of Barbadoes Gooseberry, is 

 used in the West Indies as an article of diet. That of Opuntia vulgaris 

 is known under the name of Prickly Pear. The juice of the fruit of 

 some species is subacid, and has sometimes been used as a refrigerant. 

 Cattle sometimes feed on the succulent stems in dry seasons. Some of 

 the plants are noted as night-flowering (^[ 484). Cereus grandiftorus 

 expands its large white blossoms about 10 P.M. in our hothouses, and 

 their beauty lasts only for the night. Such is also the case with 

 Cereus nycticalus. A plant of the latter species, in the Glasgow Botanic 

 Garden, began to open its flowers between 7 and 8 P.M., and they were 

 fully opened at 10. The following were the numbers and sizes of the 

 various parts: 



Length of the tube of the calyx, 7 inches. 



Length of the petals, 4| 



Length of the style, 10 



Breadth of flower when fully expanded, 11 



Number of long sepals, 75 



Number of short sepals, 20 



Number of petals, 25 



Number of stamens, 400 



Number of stigmas, 15 



The size to which some of the Cactus family grow may be illustrated 

 by a specimen of Echinocactus Viznaga, imported into Kew gardens 

 from the mountains of San Luis, Potosi: 



Weight of the plant, 713 Ibs. 



Height from surface of the earth, 4 feet. 



Measured over the top from the ground on each side,... .10 feet 9 inches. 



Circumference at 1 foot from the ground, 8 feet 7 inches. 



Number uf deep angles or costse 44 



Number of spines, 8800 



In Brazil, some epiphytic Cactuses are met with ; and there are some 

 species described by Gardner as attaining a height of thirty feet, with a 

 circumference of three feet. Opuntia cochinellifera, and other species, 

 are infested by the Coccus Cacti, or the cochineal insect, which feeds 

 upon them. The plants are cultivated in what are called nopaleries, 

 for the sake of the insect, the females of which, when dried, constitute 

 the cochineal of commerce. 



