376 



D1COTYLEOONBS. 



many parietal placenta? ; the ovules are anatropous, on long and 

 curved f unicles. Fruit a berry with exendospermous seeds. The 

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



FIG. 3G3. A Etfnnocactus: a position of a leaf-lamina ; b a lateral shoot on ihe displaced 

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

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



appearance of the Cactaceaa 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 llliipsalis 

 species, which live mostly 

 as epiphytes on trees ; m 

 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. 3G9. Ediinopsis. height and 1 metre in cir- 



