anes i 
of the genus by a critical revision of the species of the Old-World, as soon as I had 
finished my work upon the American species. It will, probably, be very 
difficult to get together a similar material including type-specimens of all or at 
least of most described species, because many of these are preserved in herbaria in 
Africa, Asia and Australia, and without type-specimens an unraveling of the nume- 
rous forms is quite hopeless. Should I, however, succeed in getting a sufficient ma- 
terial of most species, I shall be very glad to continue this monograph. 
As I have tried to prove in my earlier papers on Dryopieris, that large genus 
of ferns may be divided into a number of well defined subgenera, and in the first 
part of the present monograph I have referred the tropical American species having 
a pinnatifid-bipinnatifid lamina to ten subgenera. Since that part was published 
I have examined about 3000 specimens of species which have more divided leaves, 
and these later studies have affirmed that my classification is a natural one. I 
have no doubt that those species, which are grouped together within the same sub- 
genus, belong together genetically, while, on the other hand, they are very remotely 
' related to species belonging to other subgenera. I am convinced that most, if not 
all, of the defined subgenera really are good genera such as genera are commonly 
understood. It is, in reality, quite unnatural to unite into a single genus such different 
plants as those belonging to Eadryopteris and Ctenitis and those belonging to Gont- 
opteris and Meniscium, and even the species of Eudryopteris and Clenitis, or of La- 
strea and Cyclosorus, which very often closely resemble each other in habit, are no 
doubt generically different. Although I firmly believe now, as before, that it would 
be the most natural treatment to divide the large genus into several natural genera, 
I find it practical so retain my groups as subgenera under Dryopteris. When the 
species of the Old World have been critically examined the proper time will have 
arrived to split up the “genus” Dryopteris into genera. In this work I, therefore, 
follow my earlier classification with some minor changes. The order of the subge- 
nera I have altered, and I have referred Glaphyropteris to Lastrea as a special group, 
this large subgenus thus becoming more sharply delimitated and separated from the 
other genera. Within the subgenus Cienitis I have - changed the order of numbers 
of the species so as to bring those species which are naturally related close to each 
other, and finally, I have in this work defined two more subgenera, so that all 
American species are now referred to eleven subgenera. In a special list I have 
enumerated all species known to me in the order which I think must be consid- 
ered the most natural one. The number of the species in the descriptive part is 
the same as in the list referred to. 
a My studies of the more divided species of the genus have shown, however, 
‘that not all of these species can be naturally united with the subgenera 
