72 



On the Fossil Plants of the Coal-measures. [May 18, 



rounded, and the two flanking ones acute. The internal cavity of the 

 endotesta is prolonged like a narrow fissure only into each of the three 

 principal ridges. The ordinary sandstone specimens of Trigonocarpum 

 olivcBforme commonly seen in cabinets do not represent, as has hitherto 

 been supposed, the exterior of these seeds, but are casts of the interior 

 of the sclerench^matous endotesta, the three thin, longitudinal, wing-like 

 appendages being merely casts of the three slit-like extensions of that 

 interior just referred to. These slits extend upwards into the prolonged 

 micropyle, the interior of which displays a triangular section, each of the 

 sides of which is convex, the convexity projecting inwards. 



The nomenclature of this type of seed is in great confusion, owing to 

 specific differences being based on mere differences of size, many of which 

 are probably nothing more than varieties due to age and development. 



Casts of seeds with six longitudinal wings are described, corresponding 

 with Brongniart's genus He.vajjterosjjermum. They are more oblong 

 th&Ti '^rigonocarpum olivceforme, but apparently identical with the T. 

 Noggerathi of the ' Fossil Flora.' The author doubts the wisdom of Brong- 

 niart's establishment of a separate genus for these seeds. 



Several species of the important genus Cardiocarpum have been 

 obtained displaying the internal organization of these remarkable seeds. 

 They all agree in possessing a central endosperm which is remark- 

 able for the very large size of its conspicuous parenchymatous cells. 

 This is invested by a perispermic membrane, the whole being enclosed 

 within a testa composed of two very distinct and separate layers. A 

 thin inner one, which may be identical with the nucular membrane of 

 other seeds, is entirely composed of delicate prosenchymatous cells, and 

 is prolonged into an elongated micropyle, into which the endosperm is not 

 prolonged. Externally to this is an exotesta composed of a denser 

 parenchyma. In some species this latter tissue is uniform throughout, in 

 others it is separable into a dense endotesta and a more lax parenchymatous 

 exotesta. The first species described is apparently identical with the C. 

 anomalum of Carruthers, and has a trigonous endosperm invested by the 

 two layers of testa (?), both of which are prolonged into a slender tapering 

 beak, half the entire length of the seed, and which contains the elongated 

 micropyle. Another species, designated*t7. comjDressum., has its apparent 

 testa composed (as just described) of two continuous layers. In it the mi- 

 cropyle is comparatively short, and its apical extremity is patulous or 

 trumpet-shaped. To a third very beautiful little cordato-lanceolate species 

 with a peduncle or funiculus equal in length to the seed, the author gives 

 the name of^ Cardiocarpum ButterwortJiii, after its discoverer. These seeds 

 exhibit no speciaHzed organ corresponding to the lagenostome of Lage- 

 nostoma and other seeds described. The pollen has passed down the long 

 narrow micropyle into the triangular space at its inner extremity, where 

 it came into direct contact with the endospermic membrane. It thus 

 appears that the seeds known by the name of Cardiocarpum have a very 



