SPERMATOPHYTA 



315 



2. Bennettitales 



The Bennettitales were a Mesozoic order, world-wide in distribution. 

 They ranged from the Triassic to the Upper Cretaceous but reached their 

 greatest display during the Jurassic (Fig. 258). The four principal genera 

 are Cycadeoidea, Williamsonia, WilliamsonieUa, and Wielandiella. In 



Fig. 263. Upper part of a large stem of Cycadeoidea. Some of the strobili are projecting 

 and some have fallen out, leaving cavities. The specimen is about 60 cm. high. 



spite of their many distinctive features, the Bennettitales were probably 

 direct descendants of the Paleozoic Cycadofilicales. 



Sporophyte. The Bennettitales were more diversified in habit than 

 modern cycads. Few forms exceeded 2 m. in height and most of them 

 were under 1 m. The stems of Cycadeoidea were mostly short, stout, and 

 unbranched (Fig. 263), while those of Williamsonia were tall and colum- 

 nar, often with a few lateral branches. They bore a crown of large fern- 



