VIII, c, 3 Copeland: On Phyllitis in Malaya 151 
In some groups, slight differences are constant, and can well 
be used to distinguish species. In other groups, very con- 
spicuous differences are inconstant, and therefore without any- 
specific value. We are dealing with a group of the latter kind. 
Polymorphism is one of the alleged and supposedly diagnostic 
characters of some of the published species. Its failure to ap- 
pear on a limited number of specimens supposed to represent 
other species is very poor evidence that it does not occur. I 
can collect specimens of Asplenium epiphyticum which will 
exhibit it or not, as I choose; collecting myself, I would make it 
evident, but some other collector, not knowing the fern, might 
very easily bring in a considerable number of specimens without 
any suggestion of it. 
These ferns are not unstable in frond form alone. Even 
the characters used in founding genera, so far as they exist at 
all, are not invariable on single plants. The approximation 
of the halves of the sorus, and the line between them are in- 
constant. The latter character is under the influence of the 
former, at least to some extent; if the halves are far apart, 
they assume their character of independent sori, and the raised 
line is likely not to appear. And the approximation of the 
halves of the sorus is, at least to some extent, a function of 
the conditions under which the individual frond developed or 
+ 
plant grew. If the venation is lax, the half-sori are remote; 
then the plant is a Phyllitis. If the venation is dense, as it 
may be on the succeeding frond if the weather becomes less 
favorable, the half-sori must be closer together, and the plant 
may become Triphlebia or Diplora^ according to the thorough- 
ness with which it is examined. Figs, 5 and 6 look very distinct 
from Figs, 2 and i, and it is possible that they really represent 
distinct species; but the plant from which Fig, 6 was made 
has another frond bearing sori almost as slender as those of 
Fig. 2. 
Altogether, from the specimens I have and from the plates 
which have been published, and from my knowledge of related 
polymorphous and variable ferns, the best judgment I can reach 
is that these specimens and plates represent a single variable 
and polymorphous species ; that Diplora integrifolia Baker, ^5- 
plenium Linza Cesati, Triphlebia dimorphophylla Baker, Scolo- 
pendrinm Mambare Bailey, Phyllitis intermedia v. A. v. R., the 
New Guinea ferns called Scolopendrium longifolium Presl, and 
probably Asplenium scolopendropsis F. Mueller, all are more or 
less perfect specimens, more or less adult, in characters, — ^the 
