CHAPTER III 

 CYCADOPHYTES— BENNETTITALES 



Just as the Carboniferous has been called the "Age of Ferns," the 

 Mesozoic has been called the "Age of Cycads." 



In the Carboniferous, the Cycadofilicales reached their highest 

 development and began to decline. While they were still plastic, 

 probably in the Upper Carboniferous, two great lines, which later 

 became prominent, began to differentiate from the plexus, while the 

 ancestral lines became weaker and weaker and, finally, in the Trias- 

 sic and early Jurassic, became extinct. One of the new lines is called 

 the Bennettitales; the other, the Cycadales. The Bennettitales de- 

 veloped rapidly, reached their greatest display in the Jurassic, and 

 became extinct in the Upper Cretaceous; while the Cycadales, al- 

 though not so prominent a feature of the vegetation, still flourish 

 in various tropical and subtropical regions. 



What caused the Bennettitales to become extinct, while the Cyca- 

 dales survived, can only be conjectured. Both were probably eaten 

 by the immense herbivorous dinosaurs of the Jurassic and Triassic. 

 Their leaves and trunks, the parts constantly exposed to the weather, 

 were very similar ; the flower buds of the Bennettitales would seem 

 to be even better protected than those of the Cycadales and, edaphi- 

 cally, the two groups faced the same conditions. But the covering of 

 the strobili by bud scales may not have been entirely advantageous 

 for, if the seeds were as short-lived as those of the living Cycads, 

 many of them would have died before they were shed from the plant. 

 The seeds of the Cycadales are larger and their thick stony layer 

 may have made them more resistant than the small seeds of the Ben- 

 nettitales. At any rate, one group died while the other lived. 



Many have made contributions to our knowledge of this group; 

 some to its taxonomy, some to morphology, and some to phylogeny; 

 but the name of Wieland will always be most prominently asso- 

 ciated with the Bennettitales, for he has collected more than all 



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