THE FLOWERING PLANTS. IO9 



closely related to the Selaginella of tlie present day, have 

 been the direct progenitors of the Phanerogamia. 



On account of its anatomical structure and its embryo- 

 logical development, the sub-kingdom of the Phanerogamia 

 has for a long time been divided into two large branches, 

 into the G-ymnos'peTms, or plants with naked seeds, and the 

 Angiosperms, or plants with enclosed seeds. The latter are 

 in every respect more perfect and more highly organized 

 than the former, and developed out of them onlj^ at a late 

 date during the secondary period. The Gjnnnosperms, both 

 anatomically and embryologically, form the transition group 

 from Ferns to Angiosperms. 



The lower, more imperfect, and the older of the two main 

 classes of flowering plants, that of the ArchispermecB, or 

 Gymnosperms (with naked seeds), attained its most varied 

 development and widest distribution during the mesolithic 

 or secondary epoch. It was no less characteristic of this 

 period, than was the fern group of the preceding primary, 

 and the Angiosperms of the succeeding tertiary, epoch. 

 Hence we might call the secondary epoch that of Gymno- 

 sperms, or after its most important representatives, the era 

 of Pine Forests. The Gymnosperms are divided into three 

 classes: the Coniferge, Cycadeae, and Gnetaceee. We find 

 fossil remains of the pines, or Conifers, and of the Cycads, 

 even in coal, and must infer from this that the transition 

 from scaled ferns to Gymnosperms took place during the 

 Coal, or possibly even in the Devonian period. However, 

 the Gymnosperms play but a very subordinate part during 

 the whole of the primary epoch, and do not predominate 

 over Ferns until the beginning of the secondary epoch. 



Of the two classes of Gymnosperms just mentioned, that 



