88 
HISTORY OF BRITISH FERNS. 
with Lastrea^ formed part of the genus Aspidium^ in 
consequence of their having round seed-patches covered 
by a scale. From Lastrea, however, the Polystichums are 
known by their having the scale-like cover of the sori 
circular, without a lateral notch, its attachment being by 
a little stalk in the centre of the under side ; which form 
of attachment is called peltate. To a practised eye they 
are also known by their more rigid texture, and by their 
having altogether a more spiny appearance than even 
the spinulose species of Lastrea, The P. Lonchitis, the 
alpine form of the genus, is strictly evergreen ; and the 
other species acquire this character when in a sheltered 
situation ; but if they are much exposed, the fronds will be 
killed by severe frosts. In general, they retain their fronds 
without much disfigurement from frost quite through the 
autumn, and often far into winter. The British species 
of Polystichum are three in number, one of these being very 
prolific of interesting varieties. 
The name Polystichum is compounded of two Greek 
words— po/y, and stichos, signifying many, and order ; and 
it is applied to these plants in allusion to the numerous 
regular lines of sori, which are seen distributed over the 
fronds. 
