60 



THE ARCHAEOPTERIS FLORA 



[CH. 



nervation, or less typically the pinnules are lobed, fimbriated or 

 divided longitudinally into numerous narrow spreading seg- 

 ments. Sterile pinnules occur on the main axis between the 

 insertion of the pinnae. Fertile pinnules ^ very reduced, occurring 

 on the same frond as the sterile leaflets, usually the whole or 

 part of the lower pinnae of the frond being fertile. Fertile 



Fig. 32. ArcJiaenpteris IlUchcocki, (Daws.), 

 from the Upper Devonian of United States. 

 A fertile frond. The type specimen (nat. size) 

 after White (1905). 



pinnules bearing single or grouped (2-3) sporangia, sessile or 

 shortly stalked, sporangia fairly large, fusiform or oval, ex- 

 annulate. 



Distribution. Upper Devonian to INIiddle Coal Measures. The 

 affinities of this genus will be discussed at a later stage (p. 81). 



^ Sporangia may also occur on the margins of pinnules similar to sterile 

 leaflets, Kidston (190G), p. 434, and Johnson (191 1-). 



