272 Royal Society. 



is shown to have existed at the apex of the nucleus. The trans- 

 verse sections show that the two layers of the testa, an outer soft 

 parenchymatous exotesta and an inner sclerotesta, present some 

 striking features. The exterior of the latter has exhibited three 

 principal, acute, prominent, longitudinal ridges, between each two 

 of which are three intermediate ones, the centre of these three 

 being 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 speci- 

 mens of Trigonocarpxmi olivcfforme 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 sclerenchymatous endo- 

 testa, 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 micro- 

 pyle, 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 mth six longitudinal wings are described, cor- 

 responding with Bronguiart's genus Hexapterospermum. They are 

 more oblong than Trigonocarpum olivceforme, but apparently iden- 

 tical with the T. Noggerathi of the 'Fossil Flora.' The author 

 doubts the wisdom of Brougniart's establishment of a separate 

 genus for these seeds. 



Several species of .the important genus Cardioearpum have been 

 obtained displaying the internal organization of these remarkable 

 seeds. They all agree in possessing a central endosperm which is 

 remarkable for the very large size of its conspicuous parenchy- 

 matous 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 sepai'able 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, desig- 

 nated C. compressmn, has its apparent testa composed (as just 

 described) of two continuous layers. In it the micropyle is com- 

 paratively 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 



