1917] Butters,— Studies in Ferns — Athyrium 171 
to rely entirely upon the structure of the sorus and indusium for 
generic distinctions and delimitations. This attempt is now seen to 
have resulted in an artificial system entirely comparable to the Lin- 
naean system of classification of flowering plants. In some cases, 
particularly in highly specialized groups, it resulted in bringing 
together related forms, but it often led to obvious absurdities both of 
aggregation and of separation. It naturally resulted in particularly 
illogical results in such a group as Athyrium, where the sorus is a 
peculiarly variable and unstable organ. 
The genus Athyrium Roth ex Mertens! was originally founded 
entirely upon soral characters which further investigation has shown 
to be illusory. In view of this it is not strange that botanists like 
Mettenius and Hooker should have found it impossible to maintain 
the genus, and should have considered it merely as a section of Asplen- 
ium. In 1866 and 1870, Milde, however, in two notable papers? 
showed that the lady fern and its relatives differ in several respects 
from the true Asplenia, and refounded the genus Athyrium on a firmer 
basis. He laid particular stress on the structure of the scales in the 
two genera and on differences in the vascular structure of the frond. 
He also pointed out that Phyllitis (Scolopendrium) and Camptosorus 
agree with Asplenium in both of these respects, while Diplazium, sev~ 
eral of the other genera of Asplenieae, and the more primitive genera. 
of the Aspidieae agree with Athyrium. In his second paper he confirms. 
his earlier results so far as the differences between Athyriwm and 
Asplenium are concerned, but he confesses that he is unable to main- 
tain any generic difference between Athyrium and Diplazium, and he- 
accordingly transfers a long list of species from the latter genus to 
Athyrium. 
In general, the distinctions pointed out by Milde hold very well, 
1A ief H Prof. Mert in B den Herausgeber, Rémer’s Archiv’ 
fiir die Botanik, ii. pt. 1, 105 (1799). 
Roth, A. G., comrade necro i. 58 (1800). 
Roth’s diagnostic character Though his description of the genus: 
ad eeedactes Waka cheacit Wadi tas A. Paeksaakas Sauk wes dns bien cca anced 
treated as distinct 
of the genus, and on its various European forms, which he as species, he listed. 
as Sho Sass mpccine 4 - fontanum, a genuine Asplenium with no close affinity to the lady fern. 




Athyriam. Roth's reason for placing this this fern first was evidently merely that he was arrang~ 
ing ali af the species in order, with he et renee os a 
is evident. iff 
tion. 
ge J., Das Genus Athyrium. Bot. Zeit. xxiv. 373 (1866). 
Ueber Athyrium, Asplenium und Verwandte, Bot. Zeit. xxviii. 329 et sqq- (1870). 



