154 F1LICES. 



Leptosporangiate Ferns during the periods of the Coal-measures, we know 

 on the other hand from Schenk's l researches that there were a considerable 

 number of them already in being while the Rhaetic beds were in process 

 of deposition, and that they are to be assigned to the genera Laccopteris, 

 Presl. Selenocarpus, Schenk, Andriania, F. Braun, Clathropteris, Brongn., 

 Dictyophyllum, Lindl. and Hutt., and Thaumatopteris, Gopp. The sori 

 of all these ferns are composed of a few large sporangia, and in this respect 

 they agree with Gleicheniaceae ; but each sporangium has a closed oblique 

 and unusually well-marked annulus, quite in the manner of Cyatheaceae. 

 This was fully proved at first by Schenk 2 , and it has recently been posi- 

 tively confirmed by Zeiller 3 in the case of Laccopteris. Schenk has 

 already called attention to the agreement between these characters and 

 those of the Malayan genus Matonia, which standing as it does quite alone 

 in our present vegetation and in an intermediate position between Cyathe- 

 aceae and Gleicheniaceae evidently represents an ancient type now in course 

 of extinction ; and Zeiller has shown the perfect identity of the sori of 

 Matonia and Laccopteris by placing figures of them side by side. The 

 great variety in the character of the lamina of the leaf in all these ferns 

 shows plainly how very dangerous it is to make use of this part of the plant 

 for the purposes of rational classification. Osmundaceae also seem to occur 

 as early as the Jurassic period. To this group belongs Alethopteris 

 australis, Morris, from Queensland, according to Renault 4 . Its ovoid 

 sporangia are in longitudinal rows along the course of the secondary nerves 

 of the pinnules, and are furnished on one side with a ' plaque de d^hiscence.' 

 Pecopteris Williamsonis, Brongn., from the Oolite of Scarborough is also 

 placed by Schenk 5 with Osmundaceae, and named in accordance with this 

 position Todea Williamsonis. A figure of the plant is to be seen in Lindley 

 and Hutton 6 . Schenk gives a good description of its sporangia and of the 

 spores which they contain. 



It remains only to mention the fern-fructifications in which we know 

 the external characters only and little or nothing of the sporangia ; the 

 position of such forms in the system cannot be determined with any degree 

 of certainty, except when they come from Tertiary formations and have 

 some claim to be connected with living species. 



The genus Calymmotheca, Stur appears to occur in many parts of the 

 Coal-measures, and to be represented there by numerous species. It was 

 first observed by Schimper in the Culm of the Vosges, and thoroughly 

 examined and established by Stur 7 ; and the attempt recently made 

 by Kidston 8 to separate a new genus Zeilleria from this group must in 



1 Schenk (3). " Schenk (3). ' Zeiller (8). * Renault (2), vol. iii, p. 81 ; t. n. 



5 Schenk (11), p. 168; t. 1 5, ff. 3 a, 3 b. Lindley and Hutton (1), vol. ii, t. 126. 7 Stur 



(3, 4, 5, 6). Kidston (1\ 



