128 G. R. Wieland — Cycadeoidean Flower-bud Structure. 



took place early and that cross fertilization was the rule, aided 

 very likely by motile antherozoids. The pollen may even have 

 undergone growth and development after shedding. This, at 

 any rate, is the view I earlier proposed and still hold. Since 

 then Lignier has suggested the possibility of parthenogenesis 

 in Cycadeoidea. However, this ingenious hypothesis is quite 

 entirely lacking in direct evidence. 



General Discussion. 



There yet remain several highly interesting general con- 

 siderations as to the actual significance of the mid-ventral 

 appendages that form the remarkable dome of the flower 

 before us. In the first place it is, of course, most difficult to 

 say whether this structure is, first and last, simply a result of 

 growth response due to the appressed position of the flower, 

 and thus comparable to those thousand and one modifications 

 seen in Angiospermous flowers, or whether it has antiquity or 

 otherwise indicates inherent variety of form. For my part, I 

 think the form is an adaptation filling spatial and purely 

 mechanical requirements in a bizarre side line of the cycads, 

 which I have never regarded as quite representative of the 

 race to which it belongs. Not only so, but in all the William - 

 sonia flowers in which staminate organs have been found, and 

 such have now been studied by Nathorst, Hamshaw-Thomas, 

 and myself, there is no evidence of auricnlate or extraordi- 

 narily furrowed rachides. 



But in the first place, whether the condition here described 

 is primitive or not, the vista of modification in Cycadeoidean 

 and Wiiliamsonian sporophylls is much enlarged. And once 

 more, the Cycadeoideas are seen to present analogous characters 

 to the existing cycads. For in what ultimate respect do these 

 auriculate and horn-like appendages differ from the pair of 

 horns present alike in the Ceratozamia mega- and microsporo- 

 phyll ? However one may view this point, it is clearer than 

 ever that not even on the basis of the sporophylls can we 

 separate these two groups from each other. 



Secondly, a consideration of far-reaching and fundamental 

 importance comes into view if the grooved and winged char- 

 acter of these microsporophylls is in reality primitive, or even 

 in case approximately such a condition could primitively arise. 

 For in either case, stamens being primarily homologous to the 

 megasporophylls, some light, even if we take a purely mechani- 

 cal view-point, must eventually be shed on the relation between 

 the micro- and megaspore-bearing structures in the primitive 

 gymnosperm races, if not, indeed, on that very central paleo- 

 botany problem the origin of the seed coats. 



