Ameriran Fern Journal 
Vol. 1 JANUARY 1911 No. 3 
On the genus Dryopteris 
CARL CHRISTENSEN 
us Dryopteris includes, as. delimited in ‘my 
fae Filicum, nearly one thousand species. Like : . 
most other genera of ferns, it has reached its greatest 
degree of development in the tropics; northward it ex- 
tends to Greenland and Alaska, southward to New Zea- 
land, and it is represented in almost all regions inhabited 
by ferns, the southernmost part of South America being 
a marked exception. It is scarcely to be expected that E 
ney vast number of species were all derived from the | 
same ancestors, and I have thought it possible, me a eet : 
tailed examination of a large number of species, to 
out whether the species really are all congeneric or not. nt. ae . 
I believe I have succeeded in solving this question. oe 
While older authors = a si 
Yopsana : oP 
