176 Rhodora [OCTOBER 
Osmunda.— The American royal fern differs from the European in 
the shape of its pinnules, a difference not altogether constant, but 
enough to make desirable its recognition as a geographic variety, O. 
regalis, var. spectabilis (Willd.) Gray. 
Phegopteris.— From the point of view of the new classification, 
Phegopteris has always been an artificial genus. Our four north- 
eastern species, indeed, seem, taken by themselves, to constitute a 
separable group; but when the related tropical species are taken into 
consideration, they are seen to be part of a series of forms which, in 
all other characters than the absence of an indusium, are readily 
referable to one or another sub-genus of Thelypteris. Diels, followed 
by Christensen and many others, seems to have been entirely correct 
in reducing Phegopteris to that genus; our species should be trans- 
ferred to it and placed, in the Manual arrangement, between T. 
noveboracensis and T. fragrans. 
Pteris.— Pteridium Scop. (1760), based on Pteris aquilina L., 
though slow to win recognition as a genus, is a very natural group, 
differing constantly from true Pteris in the usually double indusium, 
the anatomy of the stipe, the presence of basal trichomes instead of 
scales and one or two other minor characters. Scopoli's name should 
be taken up for our bracken. Britton! indeed, though accepting its 
segregation as a genus, retains the name Pteris for it, on the ground 
that P. aquilina is the type of the Linnaean genus. The only apparent 
reason for this is a provision in the American Code that, in the absence 
of other means of fixing a generre type, it should be chosen from species 
indigenous from the point of view of the author. There would seem 
to be a theoretical difficulty in determining what species are indigenous 
from the point of view of an author who, like Linnaeus, was describ- 
ing the vegetation of the entire world; however, this need not concern 
. followers of the International Rules. By them, the name Pteris must 
be retained for the larger, chiefly tropical group represented by Pteris 
longifolia L. 
Not only the genus Pteridium, but its constituent species, have 
been slow of recognition, probably because of lack of attention to the 
excellent characters offered by the outer indusium, basal trichomes 
and pubescence. Instead of one cosmopolitan species, as so long 
supposed, it comprises at least six in different parts of the earth. Our 
bracken of the Manual region proves to be specifically distinct from 
1 Fl. Bermuda, 419 (1918). 
