THE HISTORY OF GYMNOSPERMS 199 



vegetation consisted of these fern-like plants, and so the coal period was 

 pictured as a time of luxuriant fern vegetation, rivalling our present 

 tropics in that feature. Approximately ten years ago these fern-like 

 plants were observed to bear seeds, and the Cycadofilicales became es- 

 tablished as the most fern-like group of Gymnosperms. All of the great 

 Paleozoic " fern " groups were found involved in the seed-bearing habit, 

 until now the residuum of real ferns in the Paleozoic seems to be quite 

 small. In any event, it has been made clear that the Cycadofilicales 

 were derived from ferns ; and if so, probably all the other Gymnosperms. 

 It should be understood that the ordinary ferns of to-day are relatively 

 modern, and are quite unlike those very ancient ferns which gave rise 

 to the Cycadofilicales, and which have received the general name Primo- 

 filices. 



This ancient group of Gymnosperms resembled ferns in every im- 

 portant particular except in the seed-bearing habit. Whereas in ordi- 

 nary ferns the sporangia are borne in groups or so-called "fruit dots" 

 (sori) on the fronds, in Cycadofilicales some of the sori were replaced 

 by seeds, which makes a seed the morphological equivalent of a 

 sporangium or a group of sporangia (a sorus). The bearing of seeds 

 necessitated also the presence of structures corresponding to stamens, 

 and producing pollen. These pollen-bearing structures remained like 

 the fern sporangia (in sori), and for a long time confirmed the notion 

 that these fern-like plants were really ferns. To say that a fern-like 

 leaf must belong to a fern might be unsafe, but to say that such a leaf 

 bearing sporangia in sori must belong to a fern seemed absolutely safe. 

 And still many of these " fern sporangia " have turned out to be the 

 pollen sacs of seed plants. 



If the bearing of seeds distinguished Cycadofilicales from ferns, the 

 absence of cones distinguished them from other Gymnosperms. The 

 seeds and pollen sacs were borne as freely on the fronds as are the 

 sporangia on the fronds of ferns. In the later groups of Gymnosperms, 

 the seed-bearing leaves and pollen sac-bearing leaves (both kinds called 

 "sporophylls") became distinct from the ordinary foliage leaves, and 

 were finally compactly organized into the cone-like structure (strobilus) 

 characteristic of most Gymnosperms. But among the Cycadofilicales 

 the strobilus stage was not reached. 



The Cycadofilicales seem to have given rise to two great branches of 

 Gymnosperms, both of which are represented in the present flora. One 

 of them includes the Cycads, and therefore have been called the Cycado- 

 phytes; the other includes the Conifers, and therefore may be called 

 the Coniferophytes. The Coniferophytes differentiated from the Cy- 

 cadofilicales earlier than our records of vascular vegetation, for the 

 Paleozoic representative (Cordaitales) of Coniferophytes is distinct 

 from the Cycadofilicales as far back as records go. On the other hand. 



