CS, 
forms of other species, but, on the other hand, some of my species are veritable 
collective species, including two or several really valid species. It was to me, how- 
ever, of more importance to describe as exactly as possible all the older species than 
to create a series of new species. The chaos ruling in most collections of this 
mighty genus shows best, how many of the old species have been falsely inter- 
preted. My descriptions are, as a rule, drawn up after the type-specimen and com- 
pleted from other specimens which in details agree with it. Several species dealt 
with in this part have very large leaves, and generally only a part of a leaf is to 
be found in the herbaria; especially old specimens are very fragmentary. Only 
a comparison of a series of specimens, which agree in minute characters, can show, 
how the shape and size of the leaf are. To which “biological type” (RAUNKLER) 
most of the the species belong it is impossible to decide, because very rarely the 
stem (rhizome or caudex) is found in the herbaria and rarely the labels give any 
information of their characters, the description of which ought to be an essential 
part of any diagnosis of a plant. Field-studies in the tropics with special regard 
to the biological types of the ferns are much needed. 
Not a few of the most characteristic species from the South-American Andes 
have been collected once only, others have been rediscovered at localities far from the type- 
locality; these facts have convinced me that the valleys of the Andes are inhabited by 
several unknown species, how many I cannot say, of course, but I believe that 
more than 500 species of the genus Dryopteris, as here understood, are growing in 
America. The geographical distribution of these species is interesting, and I believe 
that several important results for the geography of plants could be gained by a 
comparative study of the distribution of the species of a genus so rich in species 
as Dryopteris. The results obtained by my studies may possibly form the subject of 
another paper. 
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