THE EVOLUTION OF PL'ANTS 



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^), 

 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). 



