63 
be, or have been, world-wide in distribution ; it should be found, in its 
essentials in the various tribes, excepting as some tribes may probably 
be derived from others, rather than directly from the primitive form ; 
and, in the more ancient tribes, it should be possible to outline the devel- 
opment of the more recent and more specialized genera from those most 
like the generalized primitive form. 
I believe that this primitive fern, through whatever stages it may 
have been evolved, from, which all Polypodiacece have been derived, was 
a terrestrial plant of humid woods, with a short, stout rhizome, with 
ample, compound or decompound leaves, the fertile and sterile not differ- 
entiated, with nonarticulate stipe, and with small, distinct, more or 
less round sori. I shall show that such ferns as these meet every demand 
laid down in the preceding paragraph. Nearly or exactly this primitive 
fern exists now in the genus Nephrodium, more particularly in the 
subgenus Lastrcea. As is true of all generalized types, it is impossible 
by any character, or any practicable combination of characters, to diagnose 
Lastrcea as’ a natural group, retaining all species which as a matter of 
highly probable genetic affinity should be included and excluding all 
plants the genetic affinity of which is very remote. Lastrcea merges into 
Goniopteris through species with a single pair of irregularly anastomos- 
ing veinlets ; or else, as at least in part is probably the case, we include 
in Lastrcea a considerable number of - species descended through Goniop- 
teris but with free veins ; in either case the natural separation of the two 
groups is not feasible. The line between Lastrcea and Pleocnemia is but 
little less vague. 
The indusium of Tjastrcea is utterly inconstant. The lines between 
Phegopteris and Dryopteris and between Goniopteris and Cyclosorus 
appear to me to be purely artificial; nor is the shape of the indusium, 
when present, invariable. It is not rarely peltate in Nephrodium immer- 
sum, just as it is sometimes reniform in Aspidium angulatum, and in the 
plant known as Mesochlaena it is diplazioid in form. Again the sorus is 
elongate, in those immediate relatives of N ephrodium urophyllum some- 
times called Meniscivm. And even the nonarticulate stipe is not a con- 
stant character, for my No. 1712 is unmistakably a Lastrcea, with as 
evidently articulate a stipe as that of any other scandent fern. While 
the fronds are characteristically compound, there are exceptions, and 
there are species, both in Lastrcea and Goniopteris, with the fronds sub- 
dimorphous. 
As N ephrodium is altogether the most generalized and indefinable 
genus of ferns, its general characters — compound, ample, thin fronds ; non- 
articulate stipe; short, stocky rhizome, and round sori — can be accepted 
as those of the most generalized, and therefore primitive Polypodiacece. 
Lastrcea is also thoroughly cosmopolitan. 
Goniopteris is more specialized, having a relatively stable frond-form, 
almost always simpty pinnate, and firmer texture. Glandular trichomes. 
