225 
Arber. — On the Past History of the Ferns . 
already, a large number of fructifications which have hitherto been regarded 
as undoubtedly belonging to Eusporangiate Ferns of the Marattiaceous type. 
Several of these have been referred to the fronds known under the names 
of Pecopteris and Sphenopteris. In some cases the sporangia are free from 
one another, though exannulate. Such occur on unreduced fronds in 
Dactylotheca ( Pecopteris ), Renaultea {Sphenopteris) > and on reduced fronds in 
Urnatopteris {Sphenopteris). Or the sporangia are not only exannulate but 
united to form synangia. Examples, borne on unreduced fronds of the 
Pecopteris type, are found in Asterotheca , Scolecopteris, and Ptychocarpus 1 ; 
on reduced fronds of the Sphenopteris type in Crossotheca 2 . 
Less than a year ago Mr. Kidston 3 showed that one of these fructifi- 
cations, Crossotheca , was the male organ of a Pteridosperm {Lyginodendron). 
It is this discovery that has raised the present questions, Are all these 
fructifications the male organs of Pteridosperms ? Did any of them really 
belong to the Eusporangiate Ferns? 
It is obviously hopeless to try to answer these problems at the present 
stage. There are many indications that the Pteridosperms were a large and 
dominant group in Upper Palaeozoic times. So far we are acquainted 
with their male organs in only one case. There is considerable reason to 
suppose that, among the fructifications mentioned above, others will be found ; 
in fact, it is difficult to imagine where else we are to look for such organs. 
Also it must be remembered that the male fructifications of the Bennettiteae 4 , 
the direct descendants of the Pteridosperms, were essentially similar to 
some of these Palaeozoic fructifications, and to those of the modern 
Eusporangiatae, as I have already indicated. Further, we know from an 
important discovery by M. Grand’ Eury 5 that at least one Pecopterid frond 
belonged to a Pteridosperm. No doubt P. Pluckeneti , among Pecopterids, 
did not stand alone in this respect. It is, therefore, not unnatural that 
suspicion should envelop some of the synangia mentioned above, which 
are borne on Pecopterid fronds. 
On the present evidence, I am inclined to think that many others, 
besides Crossotheca , of these Marattiaceous-like, Palaeozoic fructifications 
will eventually prove to be the male organs of Pteridosperms. All such 
need not, however, have been of this nature ; but at the present moment it 
seems hopeless to try and distinguish between those which were, and those 
which were not Pteridospermic c . At any rate, there are no longer such 
strong reasons for believing that the Eusporangiate Ferns were a dominant 
type of Palaeozoic vegetation. 
1 Figures of these fructifications will be found in Scott’s ‘ Studies in Fossil Botany’, and Zeiller’s 
‘ Elements de Paleobotanique ’. 
2 Mr. Kidston does not regard Crossotheca as consisting of synangia, but of bilocular sporangia. 
3 Kidston (’05 1 ), (’05 2 ). 4 Wieland (’01). 5 Grand’ Eury (’05). 
6 Mr. Kidston (’05 2 ), p. 162 , however, regards Asterotheca as a Eusporangiate Fern, and concludes 
that, at the close of the Carboniferous period, the Marattiaceae assumed a very important place in this flora. 
