THE POLYPODIES. 203 
mon beech fern and the fronds are more erect. They 
are also thinner with fewer hairs and scales. The 
crushed fronds of both species emit a peculiar ferny odour 
from the minute glands scattered over their blades. 
This odour differs slightly with the species and one 
with an acute sense of smell might bring it into use 
in identifying them. 
In the matter of range heragonoptera again shows a 
difference. It is a southern species, extending from the 
Gulf of Mexico to Canada. It has not as yet been 
found in the Old World. The angular wings of the 
rachis have suggested the specific name and also the 
common one of six-angled polypody. Specimens inter- 
grading between this and the common beech fern are 
said to be occasionally found. 
The Oak Fern. 
Should the collector in crossing a piece of rich moist 
woods find nestling among the violets, mitreworts and 
trilliums, a tiny fern with a blade “like three fronds 
in one” that would pass for a good miniature of the 
bracken, he will be warranted in concluding that it is the 
oak fern (Phegopteris Dryopteris). The rootstock is like 
that of the beech fern—slender and creeping—and the 
fronds are produced all summer. They sometimes at- 
tain a height of more than fifteen inches but are usually 
much shorter. The stipes are very slender and the 
blade triangular, ternate, and of a delicate shade of yel- 
low-green. At the top of the stipe the blade divides 
into three nearly equal, triangular, stalked divisions, each 
of which is pinnate with sessile, deeply pinnatifid, blunt- 
lobed pinne. The middle division of the blade is slightly 
the largest and the pinnules of the lateral divisions are 
