FOLYSTICUUM ACULEATUM. 
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POLY'STICHUM ACULEA'TTJM. 
This has been included by various botanists in the 
genera Aspidium and Polypodium, but all have retained 
the specific name aculeatum, prickly, on account of the 
sharp-pointed character of the teeth on the edge of the 
leafits. Some botanists consider it and P. angulare 
only different forms of the same species. In English it 
is known as the Common Prickly Shield Fern. 
Root largo, woody, enlarging very slowly, tufted, pro¬ 
ducing many coarse, wiry side rootlets. Fronds nu¬ 
merous, spreading in a circle ; their upper part shining 
dark bluish green, but paler underneath; in general 
outline spear-head shaped, sometimes broad, at others 
narrow, but always tapering to a point, and rather stiff 
when mature, though very limp when young; in height 
from two to three feet. Stem leafleted to within three 
or four inches of its base, and covered throughout with 
reddish-brown scales. Leaflets alternate, close together, 
narrow spear-head shaped, tapering to a point. Leafits 
all rather convex, alternate, the upper one next the stem 
always larger than the others, and parallel with it, 
giving the stem somewhat the appearance of being 
bordered with alternate leafits. They are distinctly, 
though rather shortly stalked, irregular arrow-head 
shaped. Towards the upper end of the leaflet they are 
joined together at their base (decurrent); the upper side 
of each is largest, sharply saw-toothed, the teeth being 
unequal, and the points so sharp as to be really prickles; 
