Fossil Plants from Lower Carboniferous Rocks. 265 
as those which had been placed by Geinitz in his Cordai- 
carpus, only in the former genus the seeds included in it 
were restricted to those of circular form, whereas in Cordai- 
carpus they might either be circular or oval-cordate. 
Cyclocarpus is now generally united with Cordaicarpus. 
From the remarks just made, it will be seen that there 
is very little difference between the generic characters of 
Cardiocarpus, Samaropsis, and Cordaicarpus, except in the 
degree of development of the keel or wing. 
As these genera are generally employed, Cardiocarpus 
would appear to have a feebly developed wing, Samaropsis 
a strongly developed membranous wing, while in Cordaicarpus 
perhaps the seeds did not possess a wing, and the apparent 
wing in their fossil state arises from the flattening of the 
pericarp, which, extending past the nucule, appears in this 
condition as a narrow surrounding wing or keel. 
It is true that Brongniart does not refer to the seeds 
being winged in the definition of his genus Cardiocarpus, but 
it is evidently for these more or less winged seeds that 
Brongniart created his genus. The tendency, however, 
seems to be to pass over Brongniart’s Cardiocarpus in favour 
of the newer genus Samaropsis, Gdppert. 
If, on the other hand, those seeds with broad wings be 
placed in Samaropsis, and those with narrow wings in 
Cardiocarpus, the difficulty arises as to where the line of 
demarcation is to be drawn. 
Zeiller gives Cardiocarpus an equal generic position with 
Samaropsis and Cordaicarpus, and he defines it as— 
Cardiocarpus, Brongt. 
Zeiller, Flore foss. d. bassin houil. d. Valen., p. 647. 
Seeds flat, in section transversely lenticular, in form 
cordate or reniform, acuminate or bluntly pointed at the 
summit, cordate at the base, surrounded by a keel more or 
less prominent, and generally formed of a hard. seed sur- 
rounded by a fleshy envelope. 
In the condition in which the seeds are usually found, 
which Zeiller places in Cardiocarpus, they have a narrow 
