CORDAITALES 



177 



Pitys is important, for it is this type of leaf which became dominant, 

 and which has persisted in living forms. 



The root. — Not so much is known about the roots of Cordaitales. 

 No roots, showing internal 

 structure, have ever been 

 found in such close association 

 with stems and leaves, and 

 agreeing so well in histologi- 

 cal details, that there is no 

 doubt about their connection. 

 Many of them are splendidly 

 silicified, showing even the 

 cambium and secondary cor- 

 tex, with cells lined up in rows 

 as definite as those produced 

 by a phellogen in a living 

 plant (fig. 186). 



An older root, assigned to 

 Cordaiies, shows definite 

 growth-rings (fig. 187), This 

 specimen has tetrarch primary 

 wood; in others, the primary 

 wood is diarch. 



The protoxylem has spiral 

 markings, the metaxylem is 

 scalariform, and the secondary 

 wood has multiseriate pitted 

 tracheids like those of the 

 stem. 



THE SPOROPHYTE — REPRO- 

 DUCTIVE 



As in other fossil plants, 

 not so much is known about 

 the reproductive portion of 

 the life-cycle. 



The strohili. — Some of the Cordaitales are monoecious and some 

 dioecious, but there are none of the bisporangiate strobili which are 



Fig. 188. — Cordaianthiis gemnifer Grand 

 d'Eiiry: female fructification of Cordaiies 

 from Mazon Creek, Illinois, U.S.A. — From 

 NoE, Pennsylvanian flora of Northern Illi- 

 nois.*^^ 



