2g6 
THE FERN WORLD 
consequence of the lowest pair of pinnae being much larger 
and more developed than the pairs above them. Like JDryop- 
teris, too, the lower pinnules — nearest the main rachis — on 
the lowest pair of pinnae, are longer than the upper ones, and 
the point of the rachis where the lowest pair of pinnae join 
it, when they are exactly opposite, is thickened into a notch 
or joint. Some other points of resemblance will be noticed 
in the following details of description. The fronds grow 
from their creeping rhizoma to a length of from four inches 
to ten, occasionally exceeding ten inches. The stipes, which 
is furnished with a few scales at its base, is usually twice as 
long as the leafy part of the frond. The shape of the latter 
is somewhat triangular, or more strictly four-sided, from the 
circumstance of the lowest pair of pinnae being bent upwards 
out of a right angle. The lowest pair of pinnae are much 
more divided than the higher ones, being what is called 
tri-pinnate, or three times divided. They are usually, but 
not always, set on to the rachis exactly opposite. But the 
succeeding pairs are sometimes arranged in irregular alterna- 
tion. Commencing with the lowest pair of tri-pinnate pinnae, 
it will be noticed that their lower pinnules, next the main 
rachis, are much longer than the upper ones, are of an 
oblong, egg-shaped form, tapering to a blunt point at their 
apices, and are divided into a series of egg-shaped secondary 
pinnules, which in their turn are again divided into slightly 
notched or toothed lobes. All the pinnules on the lower- 
pinnae have much the same general form, differing, however, 
in size. The lower pinnule standing second on each pinna is 
also longer than the one above it. But the proportionate 
difference between upper and lower pinnules becomes less and 
less away from the main rachis, until towards the apices of 
the pinnae the opposite pinnules become equal in length, 
finally becoming merged. A somewhat similar difference 
between upper and lower pinnules is also to bo noticed on 
