SECT. II 



PHANEROGAMIA 



571 



is a herb attaining the lieight of a metre, with opposite, broad leaves and rose- 

 coloured flowers. The saponin contained in all parts of the plant renders it 

 poisonous (Fig. .551). 



Family 4. Aizoaceae ('"). Perennial herbs or small shrubs, usually with suc- 

 culent leaves. Flowers hermaphrodite ; with simple perianth or with a caly.\ and 

 a polypetalous corolla derived from modified stamens. Stamens numerous. Carpels 

 2-00 ; united to form a superior or inferior, septate ovary. Fruit a capsule. 



Xerophytic plants of hot countries. Meserribryanthemum ; a large genus, 

 especially in Africa. 



Family 5. Cactaceae (^'').— For ,?^d\^ f^ 



the most part leafl£S&-plaiit3_-with 

 succulent stems, nativesof America. 

 In size they range from very small 

 to gigantic forms. Flowers her- 

 maphrodite, actinomori)hic, less 

 commonly dorsiventral. Perianth 

 of many members, spirally ar- 

 ranged and showing a gradual 



transition from the calyx to the 

 corolla. Stamens and carpels 

 numerous. Ovary inferior, uni- 

 locular, with numerous parietal 

 placentas. Ovules with long stalks. 

 Fruit, a berry, the succulent tis- 

 sue being largely derived from 

 the stalks of the seeds. 



Peireskia and some species of 

 Opuntia possess leaves. Other 

 species of Opuntia have flattened 

 branches. Cereus, Echinocactiis, 

 with longitudinal ridges on the 

 stem ; Mammillaria has free pro- 

 jections (mamillae). The numer- 

 ous groups of spines on the shoots, 

 ribs, or separate mamillae corre- 

 spond to axillary shoots, the sub- 

 tending leaves of which are re- 

 duced, while the leaves of the expanded axis of the axillary shoot are metamor- 

 phosed into spines (Fig. 552). 



Cactaceae form a dominant constituent of the vegetation in the dry south- 

 western regions of the United States and in Mexico. They are also widely dis- 

 tributed in the West Indies and South America. A similar habit is found in some 

 Euphorbiaceae and Asclepiadaceae living under corresponding climatic conditions. 

 There are numerous epiphytic Cactaceae, especially species ot'Ilkijisalis, Epi2)hyllum. 

 and Phyllocadus, which clothe the branches of trees and afl'ect the general aspect 

 of the vegetation. 



Opuntia Jicus indica has become naturalised in the IMediteri'anean region. The 

 fruits of this species and of others of the genus are edible, and the plants are 

 cultivated as fruit-trees. Some Cactaceae, such as Anhalonium, contain highly 

 poisonous alkaloids and saponine. The Cochineal insect is grown upon species of 

 Opuntia and Nopalca {N. coccinellifera). 



Fio. 552. — Cereus geometrizans. Two of the ribs or 

 ridges of a five-ribbed stem bearing flowers and fruits 

 (J nat. size). 



