CORDAITALES 



173 



of cells, and the dehiscence is longitudinal. The stalk is traversed 



by a single vascular strand which sends a branch to the base of each 



sporangium. There is no evidence that the stamens arise from the 



axils of bracts, but the two 



structures seem to replace 



each other; in fact, the 



stamen stalk is very little 



modified from the bract 



form. In Cordaianthus 



Saportanus the stamens are 



fewer in number, being 



restricted to the apical region 



of the strobilus, and the 



stalks are shorter. 



It is evident that this 

 strobilus is to be interpreted 

 as a mixture of sterile and 

 fertile microsporophylls. If 

 the sterile sporophylls were 

 suppressed, the general con- 

 dition of the staminate stro- 

 bilus of Ginkgo would be 

 attained, but the sporangia 

 of that form are borne 

 differently. This interpreta- 

 tion implies that the stami- 

 nate strobilus of Cordaitales 

 is a simple one, and that the 

 stamen stalk is a filament. 

 The suggestion that each 

 stamen is a "flower," and 

 that therefore the stamen 

 stalk is a branch (pedicel), 



is an attempt to interpret this strobilus by the staminate strobilus 

 of Gnetales or by certain types of angiosperm inflorescence, an 

 attempt which singularly disregards the sequence of evolution. 



The terminal and erect microsporangia of Cordaitales were 



Fig. 205. — Cordaianthus Penjonii: longi- 

 tudinal section of staminate strobilus, .showing 

 microsporangia borne on long stalks; through- 

 out the sporangium region, but especially below 

 it, are numerous sterile bracts; Xio. — After 

 Renatjit (3). 



