CACTACEiE. 501 



sometimes irregular, inserted at the orifice of the calyx. Stamens in- 

 definite, cohering more or less with the petals and sepals ; filaments 

 long, filiform ; anthers ovate, versatile. Ovary fleshy, inferior, unilo- 

 cular ; style filiform ; stigmas numerous ; ovules oo , attached to parie* 

 tal placentas, equal in number to the stigmas. Fruit succulent, 1- 

 ceUed. Seeds oo , parietal, or, after losing their adhesion to the 

 placenta, nestling in pulp, ovate or obovate ; albumen ; embryo 

 straight, curved, or spiral ; cotyledons thick, leafy, sometimes nearly 

 obsolete ; radicle thick, obtuse, next the hilum. — Succulent shrubs, 

 with peculiar angular or flattened stems, having the woody matter 

 often arranged in wedges. Leaves usually ^.bsent ; when present, - 

 fleshy, smooth, entire or spinous. Flowers sessile, sometimes showy. 

 They grow in hot, dry,, and exposed places, and are natives chiefly of 

 the tropical parts of America. Some grow rapidly on the lava in 

 volcanic countries. There are two tribes : — 1. Echinocactese, calyx 

 tube produced beyond the ovary, stem with tuberculated ribs, or with 

 elongated aculei. 2. Opuntiese, calyx tube not produced beyond the 

 ovary, stem branching, articulated. There are 13 known genera and 

 about 1000 species. Exatrvphs — Opuntia, Melocactus, MammiUaria, 

 Echinocactus, Cereus, Epiphyllum, Pereskia, Ehipsalis. 



The plants of this order are remarkable for their succulence, for 

 the great development of their cellular tissue, and the anomalous forms 

 of their stems, some of which attain a great size. In their structure 

 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 

 remarkable tendency to spiral development. The setre, spines, and 

 hairs, are sometimes arranged spirally, and in Germs flagelliformis the 

 cells of -the setse have this tendency. Many of them yield an edible 

 fruit, which is sometimes refreshing and agreeable, at other times 

 insipid. The fruit of Pereshia aouleata, under the name of Barbados 

 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 (p. 262). 

 Cereus grandiflorus 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 G. MacDonaldice and G. 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 follow- 

 ing were the numbers and sizes of the various parts : — 



Length of the tube of the calyx ... 7 inches. 

 Length of the petals ih >i 



