POLYCARPICJE. 377 



cumferetice, as in G. giganteus in New Mexico) or climbing by roots 

 (Cereus and Ithipsalis-species) ; in others again, compressed, more or 

 less leaf-like, often with a ridge in the centre (winged), branched 

 and jointed : Epiphyllum, Pliyllocactus, Opuntia, some species of 

 Ehipsalis ; others are thick, short, spherical or ovoid, unbranched or 

 only slightly branched, and either studded with prominent warts 

 (mammill(E) each of which supports a tuft of thorns (Fig. 368 A ; 

 Mammillaria and others) or with vertical ridges, separated by 

 furrows (rows of mammillae which have coalesced) in Melocactus^ 

 Echinocactus, Echinopsis (Fig. 369) ; at the same time the ovary in 

 some is embedded in the stem so that leaves or leaf-scars, with 

 tufts of thorns in their axils, may be observed on the ovary just as 

 on the stem. The flattened shoots of the Cactacea3 are formed 

 in various ways, either by the compression of cylindrical axes 

 (Opuntia) or, as in Melocactus, etc., from winged stems in which 

 all the wings are suppressed except two. 



The thorns are produced directly from the growing points of the axillary 

 buds, and are modified leaves. The axillary bud is united at its base with 

 its subtending leaf, which as a rule is extremely rudimentary ; and these 

 together form a kind of leaf-cushion, larger in some genera than in others. 

 This leaf-cushion attains its highest development in Mammillaria, in which it 

 is a large, conical wart (see Fig. 368 A), bearing on its apex the tuft of thorns 

 and rudimentary lamina. The seedlings have normal cotyledons and a fleshy 

 hypocotyl. 



All the species (1,000?) are American (one epiphytic species of ftldpsulis is 

 indigenous in S. Africa, Mauritius and Ceylon), especially from the tropical 

 table-lands (Mexico, etc.). Some species, especially those without thorns, as 

 Jihipealw, are epiphytes. Opuntia vulgaris, the fruits of which are edible, is 

 naturalized in the Mediterranean. The cochineal insect (Coccus cacti) lives on 

 this and some closely allied species (O. cocchiellifera, etc.), particularly in 

 Mexico and the Canary Islands. Several are ornamental plants. 



Family 9. Polycarpicae. 



The flowers as a rule are $ , regular and liypogynous ; however in 

 some orders they are unisexual, e.g. in the MyristicaceaB, or 

 zygomorphic (in Monkshood and Larkspur in the Ranunculaceoe) ; 

 in the Lauracere, (Fig. 386) for example, perigynous, and in 

 Nymph&a (Fig. 383) even partially epigynous flowers are typical. 

 The flowers are acyclic in very many of the genera of the two first 

 orders, if not completely so, at any rate in the numerous stamens 

 and carpels, thus denoting an old type. It is a remarkable 

 characteristic that in the majority of the orders the number 3 pre- 

 vails in the calyx and corolla ; the number 5 also occurs, but the 



