386 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
occurs among Lycopods, though probably not in the form of super- 
posed whorls. In the prevailing simple structure, both of the leaf 
and of the reproductive apparatus, the Lycopodiales differ widely 
from the Sphenophyllales. In these characters as well as in other 
respects the Lycopods constitute a wonderfully homogeneous group, 
so neatly rounded off as to give little hold for any hypothetical link 
with other classes of plants. Sigillariopsis, with its double foliar 
bundle, departs in some degree frem the typical simplicity of struc- 
ture, but there is not the slightest reason for regarding this pecul- 
larity as an ancestral character. 
In certain respects the Psilotales tend to connect Sphenophyllales 
with Lycopods, for while anatomy and morphology alike indicate a 
nearer affinity with the former, some relation to the latter may no 
doubt be traced in the anatomy and habit. In spite of this, the Ly- 
copodiales remain a very isolated class, and though some connection 
with the ancient phylum represented by the Sphenophyllales appears 
probable, the common stock must le very far back. Whether the 
simple relation between sporangium and sporophyll which character- 
izes the Lycopod series is native or acquired, may be left an open 
question. The analogy of the Psilotales rather suggests the latter 
alternative, and all comparative morphology teaches how often pro- 
gress consists in simplification. 
On the other hand, while not agreeing with Professor Lignier as 
to the isolation of the Sphenophyllales from the Psilotales and their 
close affinity with the Filicales, I admit that a relation between the 
Sphenophyllales and primitive Filicinee may be conceded as prob- 
able. Though the main divisions Lycopsida and Pteropsida have 
been adopted here as convenient associations, I am inclined to extend 
the synthetic view of the Sphenophyllales so far as to admit that 
they retained some characters, such as the venation of the leaves, 
common to the Filicinean phylum. 
B. Preropsipa. 
V. FIIcALes. 
There is no part of fossil botany in which there have been such 
revolutionary changes within a very short period as in the question 
of the position of Paleozoic Ferns. Till within the last three years 
the Ferns were universally regarded as forming one of the dominant 
classes of Paleozoic plants—in fact, the most dominant of all—and 
this estimate of their importance will be found in all the text-books. 
According to the computations of systematists the Ferns constituted 
almost exactly one-half of the known Carboniferous flora. The 
position has now so completely changed that Professor Zeiller, than 
whom there is no higher authority, wrote, in August, 1905, that the 
