I04 The Ohio Naturalist. [Vol. XIII, No. 6, 



With the foregoing views as a basis for our reasoning on the 

 phylogemy of the gyninospernis, we may regard the hypothetical 

 relationships of the various classes and other groups as follows : 



The Pteridospemiae were a class of fern-like seed plants, 

 derived from a heterosporous ptenophyte group, not yet dis- 

 covered, leading off from some primitive eusporangiate, homos- 

 porous type long before Devonian times. These homosporous 

 ferns must haA^e had characters somewhat like our living Marat- 

 tiales. 



The Cycadeae are a more highly specialized branch, derived 

 from the same primitive stock as the Pteridospermae. The 

 Strobilophyta must also have been derived from the ancestral 

 type which gave rise to the Cycadeae and Cordaiteae, but did 

 not originate directly from either group. There is no satisfactory 

 evidence that the Coniferae came from the Cordaiteae. but the 

 two groups may have had a common ancestry segregated from 

 some primitive Pteridosperm stock. 



The Ginl<goeae seem to connect directly with the Cordaitales, 

 but the latter are still too imperfectly known to make a comparison 

 certain. As to the origin of the Geneteae, there is little evidence 

 They must have been segregated in very ancient times from the 

 early Strobilophyta, probably before the various groups composing 

 the phylum had received their present distinguishing characters. 

 They may have been segregated from the Strobilophyte phylum 

 soon after the Anthophyta had been segregated from the same 

 primitive stock as the typical Strobilophyta. 



The Anthophyte phylum must have been separated long 

 before it had advanced to its present unique morphology ; perhaps 

 at the very beginning of its seed bearing habit. The enlarged 

 vessel-like tracheids of the Gneteae and other supposedly angio- 

 sperm characters must be regarded as merely analogous develop- 

 ments and not as indicating a direct line of ancestry for the 

 Anthophyta. 



The synopsis of the living Gymnospermae follows below, 

 being carried out as far as the ordinarily recognized genera. Some 

 of the families, as for instance the Pinaccae, present a very striking 

 series of progressive developments and specializations. This is 

 shown in the specialization of the leaves, dwarf branches, ovuli- 

 fcrous scales, carpellate bracts and other structures. 



Beginning with such forms as Araucaria imbricata, as approach- 

 ing the more primitive organography, and then passing through 

 the Pinaceae, one finds a progressive tendency which finds its 

 highest expression in Pinus. In the genus Pinus one can again 

 find a considerable range of advancement. In Araucaria im- 

 bricata there is but one type of leaves and one type of branch; 

 in Pinus there are four kinds of leaves and two kinds of branches 

 and the dwarf branches are specialized to the extreme limit. The 



