THE SMOOTH THREE-BRANCHED POLYPODY. 87 
produced about April, and in succession through the summer, and 
perishing early in autumn. 
The nearest affinity of this species is with P. Robertianum, from 
which some botanists do not think it distinct. It can, however, 
hardly be supposed that those who have seen tolerably good living 
examples of both kinds, can adopt this opinion. P. Dryopteris 
differs from P. Robertianum in having a loosely spreading habit, 
while the fronds of the latter are rigid and erect, with stouter stalks 
and ribs, and a less membranaceous texture ; it differs further in 
having ternate or three-branched fronds, which is not strictly the 
case with the latter, although by a misapplication of terms it is 
sometimes so described. P. Dryopteris is decidedly three-branched, 
as its vernation, compared to three little balls on slender wires, | 
certifies; whilst in P. Robertianum, as Mr. Newman well states, 
the three corresponding portions of the frond never assume this 
appearance, but on the contrary, every pinnule is rolled up into a 
little globe, the pinne rolled in on their rachides, and the entire 
frond upon its rachis, so that the frond is of the ordinary bipinnate 
structure. Of less botanical importance perhaps, but equally, or 
still more clearly available as a distinguishing characteristic, is 
the perfect smoothness of P. Dryopteris, compared with the glan- 
dular pubescence of P. Robertianum, most readily seen on the 
stipes and rachis, but equally occurring over the whole plant. 
These peculiarities, which are perfectly constant in a state of culti- 
vation, mark the plants as abundantly distinct. 
Most writers describe a cruciform figure as being formed by the 
basal pinnules of the opposite sessile pinna in P. Dryopteris ; and 
it is sometimes figured, as in Mr. Newman’s work, in a very marked 
manner. Some approach to this arrangement is indeed at times 
observable, but even extensive suites of specimens may fail to 
show it in any remarkable degree ; and when it does occur, two of 
the four pinnules (the upper pair) are smaller, and nearly parallel, 
while the lower and larger ones are divergent. 
This Fern, though not a common plant, is widely dispersed in 
Great Britain. It occurs principally in wild and mountainous 
rocky districts, in the neighbourhood of waterfalls, and in the drier 

