GS 
REVUE BRYOLOGIQUE 
M. hymenophylloides was only a rock-crevice form of M. hymeno- 
 phyllum. 
it will perhaps be clearer if I tabulale the differences, as given F0 
in the descriptions, between the Lwo plants, and then deal with 
these serialim. 
M. hymenophyllum | M. hymenophylloides 
(a) Leaves arranged all round (a) Leaves of sterile stems sub- 
the stem.  complanate in two rows. 
(b) Leaves decurrent. (b) Leaves scarcely decurrent. 
(e) Stem section without ‘* fals- (c) ‘* Falsche Blatt-spuren” pre- . ne 
che Blatt-spuren ”. sent. À 
(d) Paraphyses of © f. clavate. (d) Paraphyses of © f1. filiform. 
In addition to the above, one or two minor distinctions are 
sometimes given, but as different authors do not agree upon them 
they may be disregarded here. 
a). The disposition of the leaves on the sterile shoots of M. 
hymenophylloides, giving the stem the frond-like appearance from 
which the specific name is derived, is no doubt its most distinet 
character, but it is without doubt the direct result of the light 
conditions. It is distinetively a plant of rock-crevices, anditisa 
commonplace of botanical biology that the conditions of illu- 
mination under these cireumstances tend towards à compla- 
nate, two-ranked foliation. The same condition is shown by. 
M: hornum and M. serratum. as well as by many Hypnoid 
mosses, when growing in caves or rock-crevices under simi- 
Jar circumstances. I have recently had a vave-form of Mniobryum 
albicans sent me from Ireland, showing à remarkably com- 
planate foliation. That the stems bearing inflorescences do 
= not show this character or only in a slight degree, is probably 
only another way of saying that under the abnormal light condi- 
tion of deep crevices the plant remains sterile, and only producespo 
_ flowers when these conditions are less extreme. It is probably 
_precisely analogous to the difference between the foliation of the 
fertile and sterile stems of #. affine and its allies, where the 
erect fertile stems show a normal foliation, and the more or less “3 
_prostrate sterile ones assume à dorsi-ventral position, with two- 
ranked, complanate leaves. As a matter of fact specimens Of 
M. hymenophylloides which 1 gathered at Maristuen, Norway, 
in 4900, with numerous o flowers, show very httle difference 
(except in the floral leaves themselves) between the foliation of 
the fertile and the sterile stems, the lower leaves being complanate 
in varying degrees of regularity, in nearly all, though more exactly 
in sterile stems. 
ere 
