392 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
of Fern-like seed plants. Whether this surprising similarity is 
merely a case of “ parallelism of development,” as Mr. Arber suggests, 
or is indicative of affinity, must be left an open question. <A direct 
affinity seems improbable, but it must be remembered that in Corynep- 
teris we appear to have the sporangia of Botryopteridex grouped in 
synangia like those of Marattiacee, and it is possible that in 
Sturiella (fig. 8, D) we may have another case of the same kind. It 
is therefore a not improbable conjecture that Marattiacez and Pterido- 
spermes may owe their synangic fructifications to common descent 
from a primitive group of Filicales in which the character had al- 
ready appeared. 
From what has been said above, it will be evident that our knowl- 
edge of Paleozoic Ferns is now in a transitional and somewhat un- 
satisfactory condition. The old ideas of their predominance have 
gone, never, probably, to return. There is no longer any presumption 
that a Fern-like frond really belonged to a Fern; even where some 
-of the reproductive characters seem to point the same way, the infer- 
ence, as we see in the case of Crossotheca, may be quite fallacious. We 
now have to seek laboriously for evidence, which formerly seemed to 
lie open to us on all hands. I believe, however, that such careful in- 
vestigation will result in the resuscitation of the Paleozoic Ferns as 
a considerable, though not as a dominant group. The petrified mate- 
rial, on which we now have chiefly to rely, indicates the presence of 
true Ferns,* not only in the Upper but in the Lower Carboniferous, 
and if this is so there is no reason to doubt that they extended back 
as far as any Vascular Plants. Eventually we may hope to be able 
to recognize them in the form of impressions, though now it is only 1n 
rare cases that we can distinguish such specimens with certainty from 
the foliage of Fern-like Spermophyta. 
At present our knowledge of the Paleozoic Ferns centers in the 
eroup Botryopteridex, the type-family of that ancient Filicinean 
stock, which has now come to be of supreme interest in the geological 
history of Vascular Plants. 
VI. PTERIDOSPERME., 
In reviewing the attenuated ranks ot the Paleozoic Ferns, it has 
often been necessary to refer to the contemporary Fern-like Sperm- 
ophyta which have so largely displaced them. We have now to con- 
sider, as briefly as may be, the evidence we possess as to the nature 
and extent of the Pteridospermee and the justification of their exist- 
ence as a distinct class of plants. I do not propose to trace historically 
“¥ use this phrase, not in the limited sense in which Mr. Kidston employs it, 
but to include all Cryptogamic Filicales as distinguished from Fern-like seed 
plants. 
