136 Transactions of the Society. 



A little later, in a memoir dated 1869, but not published till 

 after the war, in 1871 (Renault, 1869), the structure of stem and 

 petiole is described, and their relations determined, in the two 

 genera Zygopteris and Anachoropteris (Z. Brongniartii and A. De- 

 caisnei). The genera are well distinguished by their petiolar struc- 

 ture, though the stem with its single vascular cylinder, recalling 

 that of some of the Filmy Ferns, is of similar organisation in both. 

 At the same time the petioles of other species of Zygopteris were 

 described. This was an excellent piece of work, and we shall see 

 to what it led. 



A few years afterwards, in 1875, Eenault announced the dis- 

 covery of a new genus, Botryopteris (Eenault, 1875), giving an 

 accurate account of the anatomy of the stem, although he had only 

 a single fragment to work with. This is, perhaps, the simplest 

 type of stem known, the vascular cylinder consisting merely of a 

 solid strand of tracheides, and affords the rare case of a Palaeozoic 

 plant differing in the direction of greater simplicity of structure 

 from its probable nearest allies in the recent flora. This, however, 

 even in the case of Botryopteris, only applies to the stem. Renault 

 further described the characteristic petiole, and, what was more 

 important, was able to identify the fructifications, dense masses 

 of large, pyriform sporangia, each with a broad, band-shaped 

 " annulus." He found that they were grouped in tufts on the 

 branches of a naked rachis, indicating dimorphism of the fertile 

 and sterile fronds. As regards the affinities of the new genus, 

 Renault pointed out, with remarkable acumen, analogies with the 

 Hymenophyllacese, Osmundacea?, and Ophioglossacese, inferring 

 that there was a relation to all three groups, and coming to the 

 conclusion that Botryopteris was intermediate between the true 

 Ferns and the Ophioglossacese. His views appear fully justified 

 in the light of later research. 



The next year (Renault, 1876) the fructifications of Zygopteris 

 were discovered, and proved to present a clear affinity with those 

 of Botryopteris, though differing in well-marked generic characters. 



In the Cours de Botanique Fossile (Renault, 1883), the two 

 genera are treated as the representatives of a distinct family, the 

 Botryopteridea?, which from that time onwards has played a more 

 and more important part in the taxonomy of the Palaeozoic flora 

 (Renault, 1891 and 1896). Although some of Renault's conclu- 

 sions, especially as to the heterospory of the family, may not have 

 been substantiated, one of his greatest services to science was the 

 recognition of this group — far more extensive, probably, even than 

 he imagined. At the present time they are regarded by many 

 authorities as the most important representatives of the primitive 

 Filicinese, which long preceded the advent of Ferns, in the narrower 

 sense, as we know them at the present day. 



