LASTRA2A HIG1DA. 
175 
LASTR/E'A RI'GIDA. 
This has been called Aspidium rigidum, A. fragrant, and 
A. spinuhsum, Lophodium rigidum. Polypodium rigidum, 
Polysticlium rigidum, and P. strigosum. It is probable, 
also, that it has been confounded with the Polypodium 
fragrant of Linnasus. It is in English the Rigid Buckler 
Fern, Rigid Shield Fern, and Rigid Lastrsea. 
Root thick, slowly-extending, tufted, with many long, 
wiry rootlets. Fronds numerous, in a tuft, varying, ac¬ 
cording to the situation, from half a foot to more than 
two feet in height. The stem of each frond is thick and 
stiff, or rigid, whence the specific name; its lower third is 
without leaflets, but thickly covered with reddish-brown, 
sharp-pointed, membranous scales; these scales extend 
up the leafieted part. General outline of the leafleted 
portion a lengthened irregular triangle. Upper leaflets 
alternate, but lower ones nearly opposite; their stalks 
much thickened where they join the stem; the leafits 
are oblong, blunt, variously but deeply lobed; lobes 
with from two to five sharp teeth, but not ending in a 
spine, with the branch of a lateral vein passing into 
each tooth. Fructification, mostly at the upper part of 
the frond, is at the first fork of each lateral vein of the 
leafit bearing it, and so forming a row on each side the 
mid vein; running together (confluent) when ripe; the 
cover ( indusium ) kidney-shaped, and attached to the lateral 
vein by a short stalk at the indentation of its kidney form, 
white at first, but afterwards leaden-coloured. This cover 
