11 



lique, dorsal, attached laterally to the one side of a vein, some- 

 times double, then opposite, one on each side the vein. Invo- 

 lucre of the same form, plane or fornicate, rarely curved or 

 hij)pocrepiform, when single opening towards the costa or 

 costule, and when double (diplazioid) opening in opposite di- 

 rections. — Ferns of varied habit and aspect, inlialAtiny tro- 

 pical and temperate climates. Caudex or rhizome short and 

 erecty or decumbent, or creeping. Fronds tufted or sparse, sti- 

 pitate, simple or more or less divided and compound. Venation 

 extremely variable, free or anastomosing. 



As may be expected, from my general observations on the genera of Ferns in 

 the previous pages, I am more favourable to the views of those who retain the 

 Linnaean or Swartzian genus Aspleniiun in its integrity, than to those of Presl, 

 J. Smith, Fee, and Moore, who in going, as it appears to me, to the opposite 

 extreme, form genera founded upon characters which a more extended acquaint- 

 ance with fern-structure show to be often fallacious. I may instance the follow- 

 ing among such as are generally adopted by modern systematists. Thamnopteris, 

 judging from the species J. Smith and Moore and Presl have referred to it, these 

 have not, all of them, "the venules united at their apices by a continuous 

 slightly arcuate marginal vein," and nothing can be more contrary to nature 

 than the separation of Anpl. serratiim from Aspl. Nidus. So close is the 

 resemblance that Raddi figures and describes the former under the name 

 of Aspl. Nidus. Some true Asplenia have partially the venation of Thamno- 

 pteris. Cceiwpteris, Berg, (or Darea, Sm.) gradually passes into Asjdeniuni, 

 and though, as Mr. Brown justly observes, the involucres are marginal, and 

 open outwards on account of the narrowness of the lobes, " intus vero, quoad 

 costam e qua vena fructifera ortum ducit, libera." In respect to D/plazium 

 and its allies, there are many species which exhibit as much of the single 

 involucre as the double, and there are all intermediate grades. This is indeed ac- 

 knowledged by Mr. Moore, who says : " The limit between it {Diplazium) and 

 As])lenium is not very definite, in consequence of some species having but few of 

 the double sori. We do not refer it back to Aspleniuni, because the genus is 

 already sufficiently unwieldy. We include in it all species which produce 

 twin sori with any degree of constancy :" while in many species nothing, as expe- 

 rience has proved to me, can be more inconstant. In regard to venation, a most 

 singular instance of its inconstancy occurs in the Callipteris elegans of J. Smith. 

 Perhaps the majority of specimens have the anastomosing venation supposed to 

 distinguish the genus. It is })rol)ably not generally known that the Diplazium 

 fraxinifolium, Wall , which has free venation, quite free in general, is identical 

 with Callipteris elegans ! Tarachia of Presl (ha})i)ily, I believe, rejected by all 

 other Pterodologists), which, by relieving the truly overburdened genus now 

 under consideration of some forty species, would, if it were clearly defined, be very 

 acceptable, is characterized by exhibiting sori of Asplenium, Diplazium, and 

 Scolopendrium. Where i)racticable, I have endeavoured to employ the characters 

 of these supposed genera for sectional or subsectional ones ; though their instability 

 very much invalidates their use even then, as I shall have occasion to remark. 



A. Thamnopteris. A marginal longitudinal vein just within edge is present, 

 with which the apices of the transverse simple or for feed veins unite, and there 

 only. Sori of Euasplenium. Fronds in all undivided. 



I. A. (Thamnopteris) Nidus, L.; fronds ample 2-G feet long 

 spathulato -lanceolate acute or acuminate at the apex tapering 



