310 PHYLUM XIV. ANTHOPHYTA 
eventually splitting open to permit the escape of the 
seeds. 
570. The flower of the Prickly Pear (Opuntia, a cactus) 
is in plan much like the preceding, but there are more 
carpels (four to eight): these are united at their margins, 
so that there is but one, many-ovuled 
cavity, with four to eight parietal 
placentae. The cup is very fleshy, and 
bears on its margin and inner face the 
_/) very many stamens, many petals and 
Fic. 188.—Opuntia, Many sepals. Cactuses are evidently 
related to the Evening Primroses, but 
are peculiar in being very fleshy, and mostly leafless. 
The stems of the Prickly Pear when young bear small 
leaves, but these soon dry up and fall off after which the 
stems are leafless. 
571. The Walnut flowers (Juglans) are small and 
diclinous, those with stamens being in drooping, cylindri- 
cal, crowded clusters, those with 
pistils solitary or in pairs. Staminate cy i 
flowers with a reduced perianth C/pY 
(calyx), and many short stamens; en) | A 
pistillate flowers with a bicarpellary — Fre. 189.—Juglans. 
pistil which is wholly covered with 
the thick cup, on the margin of which are four reduced 
sepals, and as many very small petals. The fruit is fleshy 
externally while the single seed is surrounded by a mass 
of stone tissue, as in the plum. 
572. The flowers of the Oak (Quercus) are much like 
those of the Walnut, but the staminate flower clusters 
are less dense, and the pistillate flowers are solitary in scaly 
involucres (i.e. a collection of several to many crowded 
bracts). The staminate flowers have a reduced perianth 
(calyx) and six to twelve long stamens, while the single 
