46 MR. W. MITTEN—BRYOLOGIA OF THE SURVEY 
nor would they be distinguishable from the others except by their 
leaves. The capsule of H. pilifera and H. imberbis is plicate 
when old, but this character is observable in H. Humboldtii, Hook., 
which is considered by M. Schimper to present distinctions suf- 
ficient to constitute another genus, Harrisonia, and, according to 
him, to be placed amongst the pleurocarpous mosses ; but there 
is no real difference in the position of the fertile flower in any of 
the species; and the distinctions upon which these genera have 
been propounded, when considered in connexion with those 
existing between the species of eminently natural genera, such as 
Orthotrichum and Fissidens, seem to be merely specific. The 
original position of the fertile flower appears to be terminal on 
the branches, which, producing innovations from immediately 
below it, render it apparently lateral in the more branched 
species. 
Among the species included in the genera Hedwigia, Hed- 
wigidium, Braunia, and Harrisonia, there is the closest affinity 
in the structure of the leaves and in the mode of growth, except- 
ing that H. ciliata is destitute of flagelliform branches. In the 
form of the capsule there is considerable diversity ; in Hedwigi- 
dium and Harrisonia it is short and plicate, in Braunia it is 
elongate and smooth. In all these genera the calyptra is elongate 
and cucullate, in Hedwigia it is short and mitriform; but the 
value of the genera distinguished by these characters is destroyed 
when compared with other groups of species forming the most 
natural genera, Orthotrichum and Grimmia. In the first there is 
as great a diversity in the form and plication of the capsule, and 
in the second as much difference in the calyptra of species in 
most other respects so very closely resembling each other, that 
more confusion would arise in dividing them on the strength of 
that character alone than in leaving them together. The distine- 
tions therefore between the Hedwigie, measured in comparison, 
are rather of a sectional and specific nature than generic, and the 
mere multiplication of genera serves no useful purpose. 
The position of the species composing the group here under- 
stood as Hedwigia has been variously estimated by authors. 
Miiller places them amongst his Hypnoid mosses, H. ciliata in 
his Pilotrichum, and the residue in the section Pterygynandrum of 
his interpretation of the genus Neckera. Schimper places them, 
excepting H. Humboldtii, between his families Grimmie and Pty- 
chomitri& ; but the affinity between some forms of Grimmia and 
Hedwigia ciliata is less than that existing between the flagelli- 
