138 Transactions of the Society. 



which he allotted 250 to the Ferns.* Mr. Kidston, in a more 

 recent enumeration — confined to the British Carboniferous Flora — 

 out of a total of about 330 species, refers about 100 to the Ferns ;f 

 the same proportion is approximately preserved in other lists. 

 Such estimates are necessarily very rough, for a fossil " species " is 

 something very different from what we understand by a species 

 (however we may define it) in recent taxonomy ; still, as we are 

 only concerned with relative numbers, the proportion given is near 

 enough for our purpose. 



If, then, the " Ferns " of the Carboniferous were really Ferns, in 

 the true sense of the word, their numbers would suffice to establish 

 the truth of Brongniart's description of the Palaeozoic epoch as the 

 " Eeign of the Acrogens,"$ for, of the remaining groups, the Equi- 

 setales and Sphenophylls were no doubt cryptogamic, and the same 

 holds good for a large part, at any rate, of the Lycopods, in spite of 

 recent discoveries of seed-like organs in some of them. 



The question I propose to consider this evening is the real 

 nature of the Carboniferous fossil plants commonly described as 

 " Ferns." The great majority of the specimens in question are 

 preserved in the form of the beautiful impressions of " Fern-fronds " 

 familiar to all who have looked through collections of Coal-measure 

 plants ; the characters on which such specimens are referred to the 

 Ferns are necessarily derived from the form and venation of the 

 frond, and it is on similar features that their classification has been 

 founded. A few examples of these fronds may be given, taken 

 from four of the largest among the numerous genera under which 

 they have been grouped, namely, Sphenoptcris, Pecopteris, Ncurop- 

 teris, and Alcthopteris. In all four, as well as in most of the other 

 genera, the fronds were highly compound, the rachis branching 

 repeatedly in a pinnate manner. In Sphenoptcris (pi. I. fig. 1) the 

 pinnules or leaflets are usually small and lobed, and are contracted 

 at the base, as are also their segments. The venation is acute-angled 

 throughout. The habit of the very numerous species resembles 

 that of members of the genera Asplenium and Davallia among 

 recent Ferns. 



In Pecopteris (pi. I. fig. 2), on the other hand, the pinnules have 

 almost parallel margins, and are attached to the rachis by the whole 

 width of their base — a distinct midrib is present, and the lateral 

 veins spring from it at a wide angle. The habit is most nearly 

 represented at the present day among the Cyatheaceaj, or Tree- 

 ferns. 



In Neuropteris (pi. II. fig. 3) the leaves, often of gigantic size, 



* " Tableau des Genres de Vege'taux Fossiles," in Dictionnaire Universel d'Hist. 

 Nat. Paris, 1849. 



t " Divisions of British Carboniferous Rocks, as determined by Fossil Flora," 

 Proc. R. Phys. Soc. Edinburgh, xii. (1893-4). 



X A name in use at that time for the Vascular Cryptogams, or Pteridophyta. 



