152 THE EVOLUTION OF PLANTS 



their structure and fructification, show manifest 

 kinship with Marattiacese in fact this group has 

 been regarded as the dominant family of Ferns in 

 the later Palaeozoic ages. The evidence is re- 

 markably complete; both roots and leaves are 

 found in connection with the stems, and the inter- 

 nal structure of the latter is admirably preserved 

 in a great number of different species. On fronds 

 which agree in structure with those of which the 

 bases still adhere to the stems, the fructification 

 has been discovered in numerous cases. Perhaps 

 no group of fossil plants is better known in all its 

 parts than this, though, since the discovery of 

 the Pteridosperms, certain difficulties have arisen, 

 in the interpretation of the facts. 



The stems differed from those of recent Marat- 

 tiacese in stature; the Palaeozoic forms were 

 Tree-ferns, reaching, it is said, a height of 60 

 feet. The anatomical structure was, as a rule, 

 extremely elaborate, even more so than in the 

 recent family, but of the same type. The stems 

 were enveloped in a dense mantle of roots, agree- 

 ing perfectly in structure with those of the living 

 Marattiacese. The great fronds, however, had a 

 simpler vascular system. 



The fructifications are the feature of special 

 interest. Synangia are found on the fertile fronds 

 in considerable variety. A large proportion are 

 of the circular, disc-like form now only repre- 



