THE SPLEEN WORT, 57 
receptacle, and the indusium which covers them is also attached 
laterally. This peculiarity, conjoined with a simple condition of the 
sorus, indicates the Aspleniew, among which the genus Asplenium 
itself is distinguished by its simple sori and free veins, from other 
genera, agreemg in fructification, but separated by the various 
modes of reticulation which occur in their venation. 
The genus is broken up into four sectional groups, of which, as 
already indicated, two only are represented among British species, 
namely :—§ Zwuasplenium, in which the sori are oblong or linear, and 
the veins either simple or forked, and divergent at an obtusish angle 
from a central costa, or in some exotic species dimidiately-forked 
from the one-sided development of the parts of the fronds—this 
group being exemplified by Asplenium lanceolatum and. marinum ; 
and $ Acropteris, in which the sori are linear, and the veins either 
flabellately-forked without a costa, or simple or forked at a very 
acute angle from an indistinet or evanescent costa, as represented 
in Asplenium Ruta-muraria, and its allies. The remaining groups 
are :—§ Darea, having the sori oblong, and the veins for the most part 
simple in the narrow unisoriferous ultimate segments—this group 
being well represented by the Asplenium flaccidum of New Zealand, 
and the Javanese Asplenium Belangeri (A. Veitchianum) ; and $ 
Allantodia, in which the sori are short oblong, covered by convex or 
fornicate indusia, and in some cases situated at the base of the veins, 
which are simple or forked from a costa—the group being exemplified 
by the Asplenium umbrosum (A. Aitoni) of Madeira. The sorus in 
$ Euasplenium, $ Acropteris, and $ Darea, is covered by a normally 
plane or flat indusium, quite different from the vaulted cover which 
occurs in the $ Allantodia. 
The British representatives of the section Acropteris have been 
collected into a genus Amesium, by Mr. Newman ; but the absence 
of a midvein to the fronds, which is the only tangible character on 
which this genus was based, is assuredly not of sufficient importance 
to warrant the separation of the species referred to it from the 
other forms of Asplenium. Another of the species which we retain 
in the genus, namely, fontanum, was included by: Roth in Athyrium, 
and is even now placed there by some authors, but it does not agree 
in the chief characteristic on which we rely to distinguish Athyrium, 

