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).^ 



399. Perfect and Lnperfect Flowers. — A flower having 

 stamens but no carpels, or carpels but no stamens is 



Fig. 331. — Flowers of a rex begonia; staminate 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. 



' 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.) 



