426 G. R, Wieland — American Fossil Cycads. 



as just stated, that the ovulate portion of the microspore bear- 

 ing axis is abortive. But that it was once not far previous in 

 the history of these plants strictly functional, is scarcely to be 

 questioned from the perfection with which it has persisted in 

 the presence of similar but more robust seed-bearing axes 

 which have failed to produce basally, fertile microspore bear- 

 ing fronds. This bisporangiate axis is, therefore, very signifi- 

 cant, though in a lesser degree paralleled by the even closer 

 association of staminate and ovulate organs in Welwitohia mira- 

 bilis, or Tumboa, among the existing Gymnosperms. It also 

 recalls the fact that, as suggested by Schimper (Zittel's Handbuch, 

 Palaeophy tologie II, page 247\ Cordaianthus Penjoni may have 

 borne apical ovulate structures after the manner of Welwitschia. 

 My present view of the central axis is that it represents a syn- 

 thesis of carpellary but not staminate leaves, as suggested in 

 the case of Williamsonia by Saporta (Plantes Jurassiques), 

 and that it may further be regarded as essentially a modified 

 cone. The ovulate inflorescence of these Cycads, therefore, 

 underwent far more evolution than the staminate organs by 

 which it was surrounded, the latter retaining a quite primitive 

 structure. Though as will be again noted, the case is in this 

 respect exactly paralleled from the opposite side in the living 

 Gycas, where the staminate organs are modified and arranged 

 in conical order, while the carpels have retained a very primi- 

 tive form and position. Although difficult hence to surmise 

 whether the bisporangiate axis is the most primitive condition 

 leading into the gymnosperms, it is at least clear that it occurs 

 more frequently in the older forms, and that in this group the 

 process of evolution has led away from such an axis by grada- 

 tions of monoecism and finally dioecism. 



It might be hastily said that these bisporangiate axes show 

 no more essential relationship to angiospermous flowers than 

 do the gy mnosperm strobili hitherto known. And certainly 

 the testimony of fundamental importance which they do offer 

 has mainly to do with transitional stages between the Pterido- 

 phytes and the Gymnosperms. But this suggestion is here 

 emphasized : While the staminate disk surrounding the ovu- 

 late axis of Cycadeoidea indicates primarily an evolution 

 terminating, so far as now possible to trace, in the Gymno- 

 sperms, the juxtaposition of parts is exceedingly suggestive of 

 the possibility, if not the manner as well, of angiosperm devel- 

 opment directly from pteridophytic forms. For in these 

 strobili the sporophylls are organized into a flower, as I justly 

 applied the term in Part I of these studies, foreshadowing 

 distinctly the characteristic angiospermous arrangement of 

 stamens inserted on a shortened axis about an ovulate center, 

 apical and sometimes strobilar as seen in Liriodendron. On 



