XLii] COMPARISON 149 



is no clear indication of an Acrostichoid development from the Asplenioid 

 Ferns, unless it be in the problematical genus Rhipidopteris Schott. In this 

 genus the species described as Elaphoglossuui {RJiipidopteris) flabellatinn 

 H. Chr. has foliage of the type oi Aspleniuvt ruta-niuraria, while a compact 

 development of an ex-indusiate sporophyll of the type of Pleurosoriis 

 Pozoi would form a ready basis for ap Acrostichoid development (Christ, 

 ElapJioglossum, Zurich, 1899), The spores of Rhipidopteris are recorded as 

 possessing a perispore, which is a significant fact in support (Hannig, Flora, 

 191 1, p. 338). It must remain for others to test this possible relationship by 

 exact observation. 



The genera TripJdebia Baker, Diplora Baker, and Scolopendritan L. 

 {PJiyllitis Ludwig), will be treated later, as being probably Lomarioid 

 derivatives rather than of Asplenioid relationship. 



Comparison 



The genera thus retained in the Asplenieae form a naturally coherent 

 group: there is indeed difficulty in drawing any consistent line between the 

 genera Asplenium, Athyriiiin, and Diplaziuiir. and these comprise by far 

 the majority of the widely spread species. It is characteristic of them all 

 that they maintain the individuality of the sorus. There is no evidence of 

 soral fusion: even Diplasiiun, to which such fusion has been ascribed in 

 explaining the apparently double sorus, is open to the much more probable 

 interpretation of soral extension which is here suggested. All of them may 

 be held as Dryopteroid derivatives. The general habit and the anatomy of 

 the less specialised of these Ferns fully coincide with this view. It requires 

 some experience to distinguish Athyrium filix-foeniina from the common 

 Dryopteroid Ferns in any wood without looking at the sori. The similarity 

 of the dictyostele and of the leaf-trace between the Lady Fern and certain 

 species oi Dryopteris has been noted, while Athyrium also shares with the 

 Shield Ferns their relatively thin chaffy scales, though Aspleimun and 

 Diplaziiim tend to the type with lattice-thickening, clathrate as it is called. 

 These characters together with the open venation and the general Spheno- 

 pterid-architecture of the leaves relates the Asplenieae and in particular 

 Athyrium to the Dryopteroid Ferns. 



Supported by this broad and general comparison, the soral features may 

 be expected to show some degree of similarity. The basal sori of the pinnules 

 in certain species o^ Athyrium have been shown to have the actual outline 

 and construction of those of Dryopteris. Certain genera allied to Dryopteris, 

 such as Didymochlaena, illustrate the power of spread of the sorus along the 

 course of a vein. Given this, and a possible inequality in that spread on the 



