178 Rhodora [SEPTEMBER 
Asiatic groups. As both of the genera involved are already of con- 
sidérable size,— according to Christensen’s Index, Athyrium has 85 
valid species, and Diplazium, 206,— a merging of them seems undesir- 
able unless it is absolutely required by considerations of taxonomic 
honesty. So far as American ferns are concerned, the author finds 
that Athyrium acrostichoides (Sw.) Diels shows, in the thickened walls 
of the cells of its indusium, and in its pubescence, far closer kinship 
for the ordinary type of tropical American Diplazium, than for ferns 
of the lady fern group, and the same is true of Athyrium angustifolium 
(Michx.) Milde.! It seems that it may be possible eventually, to 
limit the genus Athyrium to the lady fern and its immediate allies, 
and possibly to form two or more genera out of the more remote 
groups of Athyria and Diplazia, but careful monographic work upon 
the whole complex is very much needed at the present time. 
Finally it appears that the contact between these ferns and the true 
Asplenia is through once pinnate (or possibly entire leaved) tropical 
forms such as Diplazium semihastatum (Kze.) C. Chr. and Asplenium 
bipartitum Bory, as it is only among ferns of this general type, that any 
forms with intermediate vascular structure occur. While the larger, 
2-3 times compound Asplenia sometimes closely simulate certain spe- 
cies of Athyrium, the structural differences are always perfectly sharp 
and clean cut. 
The close resemblance of the western ferns commonly classified as 
Athyrium cyclosorum to certain European forms of A. Filix-femina, 
led to an examination of all the American and old world material of 
these species in the Gray Herbarium. From this examination certain 
conclusions were reached, which are discussed at length below. These 
conclusions are as follows: 
1. That in the eastern United States and Canada there are two 
distinct species of lady ferns, neither of which is conspecific with 
A. Filix-femina (L.) Roth of Europe. One of these two species, 
A. asplenioides (Michx.) Desv. is prevailingly southern in its distribu- 
tion, the other, A. angustum (Willd.) Presl, is prevailingly northern. 
2. That the ferns of the northwest are conspecific with the Euro- 
1 In the opinion of the author these ferns should be known as Diplazium acrostichoides 
(Sw.), comb. nov. (Asplenium acrostichoides Sw. Schrader’s Journal 1800, ii. 54 (1801), 
Asplenium thelipterioides Michx., Fl. Bor.-Am. ii, 265 (1803), Diplazium thelipteroides Presl, 
Tent. Pterid. 114, 1836) and Diplazium angustifolium (Michx.), comb. nov. (Asplenium 
angustifolium Michx., Fl. Bor.-Am. ii, 265, 1803). 
