54 I POLYPODIUM. 
dense matted mass ; it is slightly scaly, and protrudes 
black fibrous roots. The fronds grow up in March and 
April, soon arriving at maturity, and entirely perishing 
before winter. Their vernation is peculiar ; the branches 
are rolled up separately, so that the undeveloped fronds 
resemble three little balls set on slender wires. They are 
bright green, smooth, and delicate in texture ; from six 
to twelve inches high, including the stipes ; three-branched, 
each branch being triangular, and attached by a distinct 
stalk-like portion of the rachis, to the common stem or 
stipes. The stipes is usually two-thirds of the height of 
the frond ; slender, brittle, dark-coloured, and quite smooth , 
except in having a few scattered scales near the base ; it 
is lateral and adherent to the caudex. The central branch 
of the frond is the largest, and its rachis is deflexed ; the 
others stand at an obtuse angle ; thus all the branches 
become loosely spreading. Each branch is pinnate at the 
base, and pinnatifid at the apex ; the pinnae usually 
opposite, nd, especially in the central branch, themselves 
pinnate at the base, then pinnatifid, and acute and nearly 
entire at the apex. The pan- of pinnules at the base of 
each pinna are so placed, that when the pinnae are exactly 
opposite, and they are thus brought together, they stand 
somewhat hi the form of a cross, the two towards the 
apex of the branch being nearly parallel, and smaller than 
the other two which are divergent. The pinnules and 
ultimate lobes are oblong and obtuse. Sometimes the 
fronds are more compoundly divided, the pinnules instead 
of being serrated as in ordinary examples being pinna- 
tifid ; when this is so, the venation becomes more deve- 
loped. In ordinary cases, each pinnule, or ultimate lobe, 
has a slender tortuous mid-vein, from which venules branch 
out alternately, extending quite to the margin, and 
bearing the son, near then* extremity ; when the parts are 
more compound hi structure, the venules are branched. In 
some cases the son are numerous, and form a crowded line 
near the margin ; in other examples they are few and scat- 
tered. 
