376 



DICOTYLEDOXES. 



many parietal placentae ; the ovules are anatropous, on long and 

 curved funicles. Fruit a berry with exendospernious seeds. The 

 fruit-pulp is mainly derived from the funicles. The external 



A 



FIG. 363. A Echinocactus : o position of a leaf-lamina; b a lateral shoot on the displaced 

 axillary bud. B Pereskia : b a foliage-leaf on a small thorny branch which is subtended 

 by a foliage-leaf which has fallen off and left a scar(o). 



appearance of the Cactacea? is very peculiar; Pereskia, which has 

 thick and fleshy leaves (Fig. 368), deviates the least ; foliage- 

 leaves of the usual form are wanting in the other genera, or are 

 usually very small, and quickly fall off and disappear (Opuntia), 

 or are modified into thorns ; the stem, without normal foliage- 

 leaves, so characteristic a feature in this order, makes its appear- 

 ance after the two normally 

 developed cotyledons. The 

 stems are fleshy, perennial, 

 and may finally become 

 woody. In some they are 

 elongated, globose, pointed, 

 and more or less dichoto- 

 mously branched, e.g. in 

 several of the Rhipsalis 

 species, which live mostly 

 as epiphytes on trees ; in 

 others, elongated, branched, 

 globose, or, most frequently, 

 more or less angular (pris- 

 matic) or grooved and pro- 

 vided with wings, and either 

 columnar and erect (as 

 much as about 20 metres in 

 FIG. 369. Echinupsis. height and 1 metre in cir- 



