very readily seen with a pocket-lens,—a necessary aid, by
the bye, to the study of Perns.
The fronds grow from six inches to a foot' in height,
nearly triangular, with the base shorter than the sides, the
stipes about equalling the leafy portion in length. They
are partially three-branched, but the lateral branches are
much smaller than the central one, and attached to the
stipes by a more slender rachis. The lower branches are
pinnate, with pinnatifid pinnæ ; the upper branch pinnate,
with its lower pinnæ again pinnate, and the upper ones pinnatifid,
as also is the apex of the frond and of the lower
branches. The pinnules or lobes have a distinct midvein,
with simple or slightly branched^venules, near the termination
of wMch, in a marginal series, the sori are produced.
This is one of the few Perns which are found in calcareous
or chalky soils. It is rare, and local in its distribution,
being, we believe, almost confined to rocky limestone
districts, and occurring chiefly in the northern and western
parts of the island. In cultivation it does not require so
much moisture and shade as most other Perns, but a limestone
soil is not at all essential to its well-being.
The names of Polypodium Rohertianum and of Lastrea
Rohertiana have been given to this species ; and the former