THE PENNSYLVANIAN PERIOD 



649 



The Cycadofilicales. It has been determined recently that 

 many of the fern-like forms possessed structural features which 

 combine the characteristics of ferns and gymnosperms; but since 

 they were seed-bearing, they are classed with the latter. The seeds 

 were borne on leaves, in positions similar to those of the " fruit dots " 



Fig. 452. A typical Cycadofilices, Lyginodendron oldhamia. (Restoration 

 by D. H. Scott and J. Allen.) 



of ferns. One of the best-known forms is illustrated by Fig. 452, 

 which exhibits the spiny stems and leaves, the highly dissected 

 foliage, the adventitious roots, and shows the general aspect of the 

 type. The structure of their leaves "is altogether comparable to 

 that of a fairly coriaceous fern-leaflet at the present day, and indi- 

 cates that the conditions to which the structure was adapted could 

 not have been fundamentally different from those which prevail in 

 our own epoch." 1 The limits of the group are not yet known, nor 

 1 Scott, Studies in Fossil Botany, p. 326. 



