500 



PTERIDOSPERMS, ETC. 



[CH. 



the meshes are usually hexagonal and arranged as shown in 

 figs. A and B, but occasionally (fig. 335, C) they follow a more 

 steeply inclined course. 



Small leaves with a more or less distinct midrib, 2 — 3 cm. 

 in length, supply transitional stages between foliage- and scale- 

 leaves. In the true scale-leaves spreading and occasionally 

 anastomosing veins take the place of the midrib and lateral 

 veins of the ordinary frond. McCoy ^ in describing some 

 Australian specimens of Olossopteris in 1847 spoke of scale-like 

 appendages of the rhizome which he compared with the large 

 ramenta of Acrostichum and other ferns. It was, however, Zeiller ^ 



Fig. 335. Glossopteris Browniana, Brongn. (After Zeiller. x 2.) 



who first recognised the leaf-nature of these scales and ade- 

 quately described them ; additional figures of scale-leaves have 

 been published by Mr Arber^ and by myself*. The import- 

 ance of these small leaves has been considerably increased by 

 Mr Arber's discovery of associated sporangia which, as he 

 suggests, were probably borne on their lower concave surface. 



The sporangia (fig. 336) are compared by Arber with the 

 micro-sporangia of recent Cycads and with the Palaeozoic 

 sporangia described by Zeiller as Discopteris Rallii (fig. 256, D) ; 

 the latter are distinguished by the well-defined group of thicker 

 walled cells representing the annulus of true fern sporangia. 

 We know nothing as to the contents of the Glossopteris 



1 McCoy (47). 



3 Arber (05) ; (052). 



2 Zeiller (96) A. 



* Seward (9.7) A; (07). 



