104 
The Ohio Naturalist. 
[Vol. XIII, No. 6, 
With the foregoing views as a basis for our reasoning on the 
phylogemy of the gymnosperms, we may regard the hypothetical 
relationships of the various classes and other groups as follows: 
The Pteridospermae 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 have 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 Ginkgoeae 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- 
sperin 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 Pinaceae, present a very striking 
series of progressive developments and specializations. This is 
shown in the specialization of the leaves, dwarf branches, ovuli- 
ferous 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 
