part 3] FOSSIL PLANTS FBOM THE FALKLAND ISLANDS. 323 



on Glossopteris fronds. 1 A piece of the midrib is seen in fig. 17 

 (PL XXI) on a slightly larger scale. It may be that this and 

 similar forms are specifically distinct from G. indica as represented 

 by leaves with a more prominent and persistent midrib, and with 

 lateral veins less gradually inclined towards the middle line of the 

 leaf : the differences are at least sufficiently obvious to place on 

 record. A comparison of the leaf reproduced in fig. 15 (PL XXI) 

 with those figured by Dr. Halle from the Falkland Islands and 

 such types as those shown in our figs. 9 & 18, raises the constantly 

 recurring question — a question which cannot be answered with 

 confidence in the present state of our ignorance — how much varia- 

 tion in venation characters may legitimately be conceded within 

 the limits of a species ? In the two forms of leaf under considera- 

 tion we have, on the one hand, differences in the degree of per- 

 sistence of the midrib and in the inclination of the secondary veins, 

 and on the other the possession by both forms of the typical 

 G. -indica pattern made by the anastomosing venation. A fairly 

 considerable range in venation characters is generally admitted, 

 and has been demonstrated in specimens which could not reasonably 

 be assigned to more than one species. The leaf shown in fig. 15 

 (PL XXI) can hardly be referred to Gangamopteris : a midrib is 

 clearly present. It may, however, be described as intermediate 

 in venation between Glossopteris and Gangamopteris. A leaf 

 described some years ago from Vereeniging as Gangamopteris 

 cyclopteroides^ bears a close resemblance to the slightly smaller 

 leaf shown in fig. 15 : its inclusion in Gangamopteris was not 

 strictly in accord with the usual definition of the genus. Leaves 

 figured by Feistmantel from the Karharbari Beds in India as 

 Glossopteris decipiens 3 are hardly distinguishable from the 

 specimen represented in our fig. 15. As Arber 4 pointed out, 

 Feistmantel's species may be regarded as a type transitional 

 between Glossopteris and Gangamopteris. Some leaves from the 

 Raniganj Series (Damuda) of India referred by Feistmantel to 

 Sagenopteris? which should unquestionably be included in Glos- 

 sopteris, afford additional examples of the same type. A com- 

 parison may also be made with an imperfect specimen from the 

 Newcastle Beds of New South Wales, named by Feistmantel 6 

 Glossopteris gangamopteroides. Impressions from Tongking 

 figured by Zeiller 7 present an even more striking similarity to the 

 leaf shown in fig. 15. An example from Angaraland, probably 

 Permian, named by Zalessky Gangamopteris (?) angarica, 8 cannot 

 be distinguished from our specimen, and might well have been 

 identified with Glossopteris decipiens Feistmantel. 



1 Zeiller (02) pi. ii, fig. 4 ; von Brehmer (14) p. 407. 



2 Seward & Leslie (08) pi. x, fig-. 3. 



3 Feistmantel (79) pi. xviii, figs. 3-5 & pi. xxiv, fig. 6. 



4 Arber (05) p. 90. 



5 Feistmantel (81) pi. xlii A, figs, la & 3. 



6 Feistmantel (90) pi. xx, fig. 4. 



7 Zeiller (02) pi. xvi, figs. 2-5. 

 s Zalessky (12) pi. vii, fig. 2. 



