POLYPODIUM. 
77 
lateral branches of the frond take their rise, but this 
feature is much more obvious in P. Dryopteris. The 
fronds are divided so that each branch is pinnate at the 
base, and pinnatifid towards its point ; the pinnge are also 
pinnate at their base, then pinnatifid, becoming acute and 
nearly entire at the point ; the pinnules and ultimate 
lobes are oblong and obtuse. The pair of pinnules at the 
base of each pinna, close to the principal rachis, are placed 
so that when the pinnm are exactly opposite they stand 
in the form of a cross ; the two towards the apex of 
the branch being smaller than the opposite pair, and 
more nearly parallel with the rachis. The pinnules or 
lobes have a rather wavy midvein, from which the venules 
branch out alternately, being, in those of moderate size, 
simple, with a sorus near their extremity, and in those 
which are larger and more compound, branched, with a 
sorus on the lower branch. The fructification is very un- 
equally produced in different seasons and localities, being 
sometimes crowded, and at other times very sparingly scat- 
tered over the fronds. 
P. Dryopteris is not an uncommon species, but it occurs 
only in mountainous situations and the drier parts of 
damp woods : in England it is found mostly in the north ; 
