THE BRITISH FERNS.
Genüs VI; ATHYRIUM, Roth.
Gen. Chak.—Sori indusiate, short ohlong-lunate, hamate, or the
basal ones more or less equally hippoorepiform ; the receptacles
occupying the anterior side, sometimes crossing and returning
along the posterior side of the veins. Indusium of the same form,
often lacerate-fimbriate at length reflexed by the crowded spore-
cases. Veins simple or forked from a central costa ; venules free,
sometimes pinnate.
Fronds herbaceous bi-tri-pinnate, having the sori more or less
generally (the basal ones usually, rarely nearly all) arcuate.
Caudex short, erect or creeping.
This genus holds as it were a middle place between the Aspidiex,
which have punctiform sori, and the Asplenim, in which they are
Hnear. It belongs indeed to the latter group, the greater part of
the sori being elongated, and a considerable proportion of them quite
asplenioid ; but others of them clearly indicate a passage from the
straight elongate form typical of Asplenium, to the short reniform
condition characteristic of Lastrea. The first indication of this
change is seen in the curving of the upper ends of certain of the sori
near the base of the pinnules, which curving produces what has been
called a hamate or hooked form of sorus. This hooked condition of
the sorus is farther changed in the anterior basal sori of most of the
more divided forms of the common Lady Fern, to that of an equalsided
curve, resembling the figure of a horseshoe. Such equally-
curved sori come very near indeed to those of Lastrea, and there can
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