2 MORPHOLOGY OF GYMNOSPERMS 



which seemed to represent clearly the synangial habit of the Marat- 

 tiaceae. Furthermore, the anatomy of the petioles of other frond 

 genera was described as being much like that of the petioles of the 

 Marattiaceae. Such results seemed to confirm the old view that the 

 sterile frond genera were not only ferns, but also ferns of the Marattia 

 type. 



In 1887 WiLLLiAMSON (5, p. 299) first recognized "the presence 

 in the carboniferous flora of plants combining the characters of ferns 

 and cycads" (86); and in 1896 Williamson and Scott (18) 

 described the anatomy of Lyginodendron and Heterangium. In 

 the same year Weber and Sterzel (17) described the anatomy of 

 Medullosa. These are prominent stem genera, which belong to some 

 of the sterile frond genera; and these observers discovered in them 

 an anatomical structure distincdy intermediate between that of 

 ferns and that of cycads. In view of this fact, in 1899 Potonie (20) 

 named the group Cycadofilices, basing it upon anatomical features, its 

 composite character being indicated by the name. The striking 

 anatomical feature of the Cycadofilices is the association of sec- 

 ondary wood with a fernlike vascular system. There was no occa- 

 sion, on this account, to remove Cycadofilices from pteridophytes, 

 as secondary wood occurs in Sphenophyllum, Lepidodendron, Cala- 

 modendron, etc., and also in existing species of Isoetes, Selaginella, 

 Psilotum, and Equisetum. Nor would this character even remove 

 the group from ferns, for a cambium occurs in Marattia, Angiopteris, 

 Ophioglossum, and Botrychium (63). In fact, secondary wood evi- 

 dently originatied independently in many groups and at many times 

 (50), and therefore could not be made the basis of an important 

 segregation. 



In 1903, however, Oliver and Scott (39) announced that certain 

 characteristic seeds belonged to the fronds of Lyginodendron Old- 

 hamium, and the association with pteridophytes was at an end. In 

 the same paper the group name Pteridosperms was proposed, to 

 include those Cycadofilices that bear seeds. Since then other seed- 

 bearing fronds have been discovered, until now all of the prominent 

 frond genera are involved. 



Finally, in 1905 Kidston (54) announced the discovery of the 

 microsporangia of Lyginodendron Oldhamium, and all of the important 



