566 Mr. Brown on Lyellia, Leptostomum, and Buxbaumia. 



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 Poli/trichum 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 Polytricho'idecE, and is wanting 

 in Polytrichum undulatum and angustatum. But the lamellee ot 

 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 lamellae, which are represented in several of the species 

 figured in English Botany, by Wahlenberg in P. IcEvigatum*, 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 Miiscologia 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 developed and strictly 

 confined to the nerve. 



In the form and position of the male 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. ttndulatum, 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 Polytrichum, long considered as the 

 * Flora Lappon. tab. 22. t Muscol. Brit. p. 24. 



essential 



