566 Mr. Browx on Lyellia, Leptostomum, and Buabaumia. 
the order, and, from the great size of the capsules in many of its 
species, most readily admitting of accurate observation, has never 
yet been thoroughly examined. 
One of the most striking characters of Polytrichum is the dense 
texture and consequent opacity of the leaves; in which it agrees 
with the other two genera of the section. ‘This character, how- 
ever, is not altogether confined to Polytrichoidee, and is wanting 
in Polytrichum undulatum and angustatum. But the lamelle of 
the upper surface of the leaves probably exist, though in very 
different degrees, in all the species of Polytrichum; are equally 
observable in Lyellia and Dawsonia; and I am not aware that they 
have been found in any other genera of the order: 
These lamellæ, which are represented in several of the species 
figured in English Botany, by Wahlenberg in P. levigatum*, and 
since noticed by Messrs. Hooker and Taylor as existing in nearly 
the whole of the genus, do not belong to the nerve only, as the 
authors of Muscologia Britannica seem to suppose, but in several 
species cover the greater part of the surface of the upper or spread- 
ing portion of the leaf; the sheathing base being either entirely 
destitute of them, or having them much less dexcleped and strictly 
confined to the nerve. te ec git} agi | 
In the form and position of the ines: flowers there is probably 
an absolute uniformity in the whole of this group: but the only 
peculiarities consist in the perigonial leaf or bractea being formed 
chiefly of the sheathing part of the stem-leaf; and in the new 
shoot proceeding from the centre of the star-like cluster. In 
P. undulatum, however, the former character is by no means ob- 
vious, and the latter is not perhaps constant; and both are only 
presumed to exist in Lyellia. 
The double calyptra of Polyirichum, ioni considered as the 
* Flora Lappon. tab. 22. T Muscoli Brit. p. 24, — - 
essential 
LI 
