THE EVOLUTION OF PLANTS 



211 



trayful of flowers may be all the record of the Pterido- 

 sperms from the Devonian on. The gaps in the evidence 

 are always enormous." 



Although the Cycadophyta are now a very insignifi- 

 cant element in the earth's flora, in the Mesozoic period 





FIG. 95. Macrozamia spiralis. Tip of the trunk, showing three 

 lateral cones, inserted in the axils of leaves. Photo from specimen in 

 Brooklyn Botanic Garden. (C/. Fig. 96.) 



they form about one-third of the recovered vegetation of 

 the land. One order, the Hemicycadales (Bennettitales x ) , 

 then had a cosmopolitan distribution and seemingly was 

 as important as the Dicotyledons are now. Over 30 species 

 of the petrified stems have been found in the Mesozoic 



'In his paper on the Classification of the Cycadophyta (Am., Jour. Sci. 

 47: 391-406. June, 1919), Wieland states ''simple and good reasons" 

 for letting the name Bennettitales fall into disuse, and substituting there- 

 fore the term Hemicycadales (half-cycads). 



