152 THE LIVING CYCADS 



The final stage in the reduction is well illustrated by 

 Zamia (Fig. 91). There is no indication of leaflets or a 

 midrib, and the whole structure has become so flattened 

 that the two ovules seem to be borne on the under side 

 of a peltate expansion of the stalk; but even in this most 

 reduced condition the internal structure shows that we 

 are dealing with a leaf bearing ovules on its margin. 



The whole series shows conclusively how the com- 

 pact cone has been derived from a crown of sporophylls 

 which in their most primitive condition closely resemble 

 foliage leaves. 



Some may object to this statement and claim that 

 in phylogeny the spore-bearing function appeared long 

 before there were any sporophytes with foliage leaves. 

 This we readily admit. We do not know how the foliage 

 leaf originated, but in the Devonian it was already as 

 highly developed as in our living ferns. Beginning at 

 this point the sporophyll has been derived from the 

 foliage leaf and has become more and more modified, 

 until it has reached an extreme form in compact cones 

 like those of most of the cycads. 



The male cone. — The male cone is comparatively 

 uniform throughout the group. There are dift'erences 

 in size and shape, but the sporophylls are alike in being 

 more or less flattened, in showing no indication of 

 leaflets, and in bearing groups of sporangia upon the 

 under surface. Even in Cycas, which has the loose 

 crown of female sporophylls, the male cone is as compact 

 as in Zamia. 



There is a reduction as we pass from the Cycas end 

 of the group to the Zamia end, but the reduction consists 

 in a diminution in the size of the sporophylls and in a 



