KIDSTON : THE FLORA OF THE CARBONIFEROUS PERIOD. 367 
The Cordaitece, however, possess distinctive characters of their 
own, and though showing more affinity to the Cycads than to the 
Conifers, form a distinct group which cannot be united with either, 
but must be regarded as equal in importance with them. 
Seeds. 
Many isolated gymnospermous seeds occur in the Carboniferous 
rocks of which some certainly belong to the Cordaites. These, accord- 
ing to their form and structure, have been placed in many genera, as 
it is seldom ever possible to refer them satisfactorily to their parent 
stems. The more important of these genera are : — 
Samaropsis Goppert. Generally small oval seeds, lenticular 
in section, pointed at the apex and rounded or slightly cordate at the 
base, and surrounded by a more or less prominent membranous 
wing w^th a notched or acute apex (Samaropsis bicaudata Kidston, 
Plate LVIIL, figs. 5-6). 
Cardiocarpus Brongniart. Smooth flattened seeds, oval or 
circular in outline, sharp or obtuse at summit, sometimes slightly 
cordate at the base and surrounded by a more or less distinct marginal 
■\ving {Cardiocarpus cf. emarginatus Artis. sp., Plate LXL, fig. 5). 
Carpolithes Schlotheim. Smooth oval seeds, generally of small 
size, without any wing and not cordate at base {Carpolithes perpusillus 
Lesquereux, Plate LXV., fig. 4, and Carpolithes ovoideus Goppert 
and Berger, Plate LIL, fig. 1). 
Rhabdocarpus Goppert and Berger. Oval or cordate seeds 
containing a hard nucule surrounded by a more or less fleshy enve- 
lope in which are numerous hypodermic strands that impart a striated 
appearance to the outer surface of the compressed fruit {Rhabdo- 
carpus multistriatus Sternberg sp., Plate LXL, fig. 4). 
Trigonocarpus Brongniart. Hard, nut-like, oval seeds, circular 
in transverse section and provided with three prominent, and between 
them three less prominent, ridges. Before maturity the seed is 
surrounded by a large pericarp which extends considerably beyond 
the apex of the nut. 
Figs. 1 and 2, Plate LXV., show specimens of Trigonocarpus 
Parkinsoni Brongt. enclosed in the pericarp. The Carpolithes alata 
