18 . 
THE HARD PRICKLY SHIELD FERN. 
Polyst ich um a cut eatum. 
Plate 8, Fig. 3, Page 293. 
The British Shield Ferns constitute a small but beautiful 
group, possessing some very distinctly-marked characters 
which at once serve to make them recognizable. The 
generic name of Polystielmm is derived from two Greek 
words, polys, ‘many,’ and stichos, ‘order ; ’ and refers to the 
numerous lines of spore cases on the backs of the fronds of 
these Ferns, and to the regular order in which they are 
arranged. It no doubt also refers to the regular order of 
the pinnules in this Fern. The specific name of aculeatum, 
‘prickly,’ serves to distinguish the present Fern from the 
rest of the group, referring as it does to its more rigid and 
prickly nature. The common name of Shield Fern — repre- 
sented by the old botanical name of Aspidium, which was 
the generic designation of a larger group, including 
amongst others what are now the Shield Ferns, the Buckler 
Ferns, and the Bladder Ferns — refers to the mark which in 
the modern system of classification distinguishes this genus 
from others. This mark is the round, or shield-shaped 
indusia, which cover the round heaps of spore cases on 
the backs of the fronds, and are attached to the latter by 
little stalks in the centre, and on the under side of the 
scaly shields. Polystielmm aculfiitioni grows on the steeper 
sloping sides of wooded hills, and on the sides of sloping 
