MR. E. 8. SALMON ON THE GENUS NANOMITRIUM. 167 
lineam circumscribentem habentibus ideoque haud incrassatis, 
inflorescentia par-synoica, theca maxime leptodermi, fere sine 
vestigio ullo rostelli, calyptra apici thece arcte adherente, 
minima et brevissima, ut fere ad stylum solum reducta." 
Philibert (5. p. 52), as the result of a eritical examination of 
the genus, concluded that * La différence essentielle entre ces 
deux genres [Ephemerum and Nanomitrium] parait done consister 
en ce que les espéces qui appartiennent au premier ont toujours 
un sporange distinct, tandis que celles du genre Nanomitrium en 
sont dépourvues"; also remarking (loe. cit. p. 57): “Le genre 
Nanomitrium, quoique bien distinct du genre Ephemerum par la 
Structure du sporogone, n'en serait pas cependant séparé par des 
limites aussi tranchées que le supposait Lindberg: d'un côté le 
N. megalosporum se rapproche des Ephemera par le tissu des 
feuilles et la grosseur des spores, et d'un autre cóté le N. equi- 
noctiale s'en rapprocherait par l'inflorescence." 
Limpricht (6. p. 160), in his key, separates Ephemerum from 
Nanomitrium by the presence of stomata on the capsule of the 
species belonging to the first genus; also remarking on Nanomi- 
trium (loc. cit. p. 162), “zur Reifezeit Columella und Sporensack 
völlig resorbirt" ; and on Ephemerum (loc. cit. p. 164), “ Columella 
innerhalb des Sporensackes resorbirt, Sporensack bleibend und an 
beiden Polen mit kurzen Süulchen, den Resten der Columella, die 
den zur Reifezeit noch vorhandenen Luftraum durchsetzen." 
N. megalosporum shows the artificiality of the two genera as at 
present defined, for in this species the capsule has the shape, and 
perhaps the calyptra, of Nanomitrium, while its structure is that 
of Ephemerum. 
I would propose that the genus Nanomitrium, as we now know 
it, be restricted to N. tenerum, N. synoicum, and N. Austini, and 
that the essential character separating it from Ephemerum 
be the presence of a strongly leptodermous capsule (with 
a wall at maturity formed of only a single layer of cells), 
possessing a rudimentary lid, as shown by the occurrence of 
differentiated cells, by which a regular dehiscence is effected. 
N. megalosporum must be transferred to Ephemerum, and probably 
N. equinoctiale also, although more observations are desirable to 
settle this last point, 
There remains to be considered the systematie position of the 
two genera, and some of the facts mentioned above help, I think, 
to decide this question. 
Limpricht, in his admirable * Die Laubmoose," has unfortu- 
