438 



PHANEROGAMS. 



to a dichotomous branching of the leaf, the rachis of which may therefore be con- 

 sidered as a sympodium composed of the basal portions of the successive bifur- 

 cations, while the lateral leaflets represent the bifurcations of the lamina of the leaf, 

 the growth of which is arrested and flattened. The whole leaf would therefore be 

 a dichotomous cymose branch-system. Researches into the history of its develop- 

 ment are however wanting, as in the case of the branching of the stem and root. 



Fig. ^\^.—Kca.xpe\oi Cycas rez'ohita (reduced about ^);y pinnae of the leaf-like carpel; j/t ovules replacing the 

 lower pinnK ; sk' an ovule further developed. 



The Flowers of the Cycadeoe are always diclinous and dioecious ; both kinds of 

 flowers appear at the summit of the stem, either singly as in Cycas as terminal 

 flowers of the primary stem, or in pairs or larger numbers as in Zamia vitn-icata and 

 Macrozamia spiralis, where they may perhaps be regarded as metamorphosed 

 bifurcations of the stem\ The flower consists of a strong conical elongated axis, 



* The hypothesis that the male flower of Cycas Rutnphii is one, the leaf-bud by which the stem 

 is prolonged the other bifurcation of the dichotomising apex of the stem, is not supported by 

 De Bary's recent researches. 



