54. ON GENERA AND SPECIES. 



of growth and venation, but with the exception of five 

 species of Platycerium he retains the whole under the 

 genus Acrosticlium. 



Of the tribe AspleniecB he describes over 300 species, all 

 comprehended under the genus Asplenium, except two 

 species which constitute the two genera Allantodia and 

 Actinopteris. With regard to Scolopendrium, some authors 

 consider it as a genus scarcely separable from Asplenium, 

 but in the " Species Filicum " it is characterised as a dis- 

 tinct tribe under the name of Scolopendriece. It consists of 

 nine species, which agree in general habit with Asplenium, 

 and present no special character to justify their separation 

 as a tribe from Asplenieee. 



We give another instance, in speaking of Hypoderris, 

 he says : " Considering as I do that the primary divisions 

 should be taken as much as possible from the fructifi- 

 cation, I have no hesitation in placing Hypoderris among 

 the Dicksonice and near to Woodsia" No three genera 

 can be more distinct in natural affinity than these that 

 is, as regards habit and anatomical structure ; the only 

 similitude is between Hypoderris and Woodsia, which have 

 discal punctiform sori, with a very membranous cup 

 indusium, therefore in that character are more properly 

 though artificially related to Cyathea than to Diclcsonia, 

 which has marginal sori with cystiform indusia opening 

 outwards. 



Again, take the case of Matonia, a rare Fern with fan- 

 shaped fronds, in every respect allied to Gleicbenia in 

 habit, and also in the ring of the sporangia being hori- 

 zontal, and differing only from Gleichenia in the sori being 

 furnished with an inverted cup-shaped indusium, attached 

 by its centre as in true Aspidium and Polystichum. 

 Although such is the case. Sir William Hooker follows 



