304 THE ANATOMY OF WOODY PLANTS 



the basis of comparative anatomy receives strong support from 

 the organization of certain Paleozoic Cycadonlicales, notably the 

 Medulloseae. There seems to be little doubt that the genera of 

 Cycadales in the broadest sense of the term have been derived 

 from ancestors closely resembling vegetatively the Medullosa 

 type. It follows that so far as their primary fibrovascular struc- 

 tures are concerned they present a condition of reduction from 

 the anatomical organization found in the oldest and most fernlike 

 gymnosperms. 



