CORDAITEAE. 



119 



minates in the base of the nucellus, where its elements spread out in a 

 radiating manner, but it previously gives off lateral branches, usually two in 

 number, which traverse the testa till they nearly reach the micropyle. It 

 may seem strange that the egg-cells have been observed in the substance of 

 the endosperm, but not a developed embryo, though this has been seen in 

 Bennettites. The probable explanation is, that in these forms the develop- 

 ment of the embryo proceeds slowly, as is the case at the present day with 

 Ceratozamia, Ginkgo, and Gnetum, 



B 



A 



FIG. 10. Seeds of Gymnosperms from the Coal-measures. A magnified longitudinal section of Stephanpspermum 

 akenioides, Brongn. ; d endotesta ; b endosperm with two archegonia; c pollen-chamber; p pollen-grains in the 

 chamber which are seen more highly magnified at //, // ; mi micropylar end of the seed. B slightly magnified 

 longitudinal section of CardiocarpusJ sclerotesta, Brongn. ; d endotesta ; -mi micropyle ; c endosperm with archegonia ; 

 chp upper terminal portion of the membrane bounding the nucellus with the pollen-chamber in it. After Saporta and 

 Marion l . 



Brongniart 2 has distributed the seeds which he has examined among 

 different genera according to their general form and the structure of the 

 testa. Of these, Cardiocarpus, Rhabdocarpus, Diplotesta, Sarcotaxus, 

 Taxospermum and Leptocaryon are flat seeds, and they are especially the 

 forms which Renault thinks belonged to Cordaitae. The transverse section 

 of Stephanospermum and Aetheotesta is simply circular. The former 

 genus is distinguished by the extraordinary size of its pollen-chamber, 

 and its testa has a winged border forming a collar round the micropylar 

 end of the seed. In all the rest the transverse section shows three, six 

 or eight edges of wings. In Trigonocarpus there are three flat edges, 

 and the testa is fissured in the edges. Hexapterospermum, Polyptero- 

 spermum and Polylophospermum have six simple winged edges ; Ptycho- 



Saporta et Marion (2). 



Brongniart (6). 



