SEED-BEARING PLANTS 
447 
reality, a flower; or they may be megasporophylls. In 
the latter case they may occur on the main stem, as in 
Cycas (Fig. 291), or grouped on a specialized branch, 
forming a cone, as in Macrozamia (Fig. 289). 1 
399. Perfect and Imperfect Flowers. A flower having 
stamens but no carpels, or carpels but no stamens is 
FIG. 331. Flowers of a rex begonia; stamlnate above; pistillate below; 
one of the latter with the perianth removed to show the ovary and stigmas. 
(Photo by Elsie M. Kittredge.) 
unable, by itself, to produce seed, and is hence called an 
imperfect flower (Figs. 331-333). A species in which the 
imperfect flowers occur on separate plants is dioecious. 
1 Whether the carpellate cone of Pinus is a flower or a cluster of flowers 
(inflorescence), has long been debated. There is strong evidence for con- 
sidering it a cluster of flowers, since the individual scales are probably not 
simple sporophylls. (Cf., p. 419.) 
