It is a question of secondary importance whether or not the fronds which Brongniart spoke of as a variety of Glossopteris Browniana should be recognised as specifically distinct. The careful examination by Zeiller of the venation characters has, however, afforded justification for separating G. Browniana and G. indica. We must admit that the slight and not very constant differences in the size and form of the meshes produced by the anastomosing of the lateral veins are characters which cannot be recognised as having more than a secondary value, though, as a matter of convenience, we employ them as aids to determination. The arbitrary separation of sterile leaves, which differ by small degrees from one another in form and in the details of venation, by the application of specific names is a thankless task necessitated by custom and convenience; it is, however, idle to ignore the artificial basis of such separation. Mr Arber has recently published, in his valuable Glossopteris Flora, an analytical key which serves to facilitate the description and determination of different types of frond[1325].

Fig. 340.

  1. Glossopteris indica, Schimper. (½ nat. size.)
  2. Glossopteris angustifolia, Brongniart. (Nat. size.) From Arber, after Feistmantel.

The large leaves of Glossopteris indica, reaching a length in extreme cases of 40 cm. and a breadth of 10 cm., are characterised by a rather greater regularity in the arrangement of the meshes and by the greater parallelism of the upper and lower sides of each mesh ([fig. 341]) and by less difference in size between the venation meshes than in G. Browniana, the leaves of which are usually smaller. The relatively thick epidermis consists of rectangular cells with stomata in depressions[1326]. The scale-leaves[1327], rather larger than those of G. Browniana, are more or less rhomboidal with rounded angles and reach a length of 1·5–6 cm. and a breadth of 1·5–2·5 cm. The rhizome is practically identical with that of G. Browniana[1328].

Fig. 341. Glossopteris indica, Schimp. (× 1½.) From Arber, after Zeiller.

This species occurs in great abundance in the Permo-Carboniferous rocks of India, Australia, and in various parts of South Africa, and elsewhere. It has been recognised also by Amalitzky[1329] in Upper Permian beds in Russia and by Zeiller in the Rhaetic series of Tonkin[1330].

Fig. 342. Glossopteris angustifolia var. taeniopteroides. (× 3½.)