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 









■^^Ct^ 



Fig. 32. Archaeopteris Hifchcocki, (Daws.), 

 from the Upper Devonian of United States. 

 A fertile frond. Tlie 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 Middle Coal Measures. The 

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



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

 leaflets, Kidston (1906), p. 4.34, and Johnson (1911^). 



