SOME REMARKS ON THE CLASSIFICATION OF FERNS. 255 
of its affinities, as “ being analogous to the, want of indusia in closely 
allied species of Phegopterides.” The firm, coriaceous, extended, linear 
indusium of the Lomariee,—very different from the delicate and minute 
one of many Aspidia,—is, in my judgment, far too marked and im- 
portant a character to be regarded as of subordinate value ; and, fully 
persuaded as I am that our classification of Ferns will hereafter be 
profoundly modified, I believe, in the present state of our knowledge, 
that the presence or absence of an indusium is the most important and 
reliable primary character we can employ. It is true that M. Fée 
asserts (sub voce Pleocnemia) that some Ferns exist under both forms ; 
and I have myself alluded to an apparent example of this kind in 
Polypodium urophyllum, Wall.; but I suspect the truth to be that, if 
observed when sufficiently young, such Ferns would, in a state of 
nature, be found always indusiate, although the indusium is often of 
very delicate texture, and evanescent. Aspidium amabile, Bl., A. Sin- 
gaporianum, Wall., and A. coniifolium, Wall., are certainly in this 
case; and it is notorious how many species of that genus have been 
referred to Polypodium, owing to being described from old specimens. 
I have a wild specimen of Woodsia (Hypoderris) Brownit, Mett., in 
which, after the most careful examination, I have failed to detect a 
trace of involucre, doubtless from the sori being advanced in age. In 
a considerable number of Aspidia belonging to the Polystichum group, 
and sometimes in 4. javanicum, Mett., the indusium curls up, and is 
forced inwards and concealed by the overlapping sporangia, so that 
plants in full fructification appear nudisorous. If I am correct in my 
surmise that apparent exceptions to the constancy of this character are 
due to the caducous nature of the indusium, and not to its absence, 
then Polypodium urophyllum must be transferred to Aspidium, with 
many species of which, in the Nephrodium group, it agrees very well ; 
and Mr. Smith's objection would vanish. 
Assuredly, the “ Saturnia regna " in which botanists shall sit down 
with anything like aecordant views as to the absolute or relative value 
of different structural characters in Ferns, and the limits of the genera 
to be admitted, seem very far off indeed; for, whilst Professor Met- 
tenius declares that, after the most scrupulous examination, he is un- 
able to recognise the validity of the numerous genera separated of late 
years from Polypodium; M. Fée asserts the views of the analytical 
school to be so manifestly superior in forming natural groups, that 
