

The "Bryologia" of the survey of the 49th Parallel 01 ijanruae. 

 By William Mitten, A.L.S. 

 [Read Jan. 22, 1864.] . 

 [Plates V.— VIII.] 

 The Mosses collected during the expeditions for the survey of 

 the 49th Parallel owe their principal interest to the specimen 

 gathered by Dr. Lyall on the west side of the Uocky Mountains 

 and in Vancouver Island, and these contain certain species which 

 appear to be peculiar to that region, all the species from the 

 country on the east side of the Eocky Mountains having been 

 previously gathered by Drummond. Considering the vast extent 

 of British America with regard to the specimens in herbaria, it 

 becomes at once evident that but very little is yet known of its 

 Moss-flora beyond the fact that it is very nearly identical with 

 that of the north of Europe, and, so far as known, with but few 

 peculiar species. A great gap exists in British herbaria in the 

 almost entire absence of collections from all that extensive tract 

 of country between Davis's Straits, Hudson's Bay, and Nova 

 Scotia ; and as this includes a great extent of regions subject to 

 marine influences, it must be expected to produce a very exten- 

 sive series of species. 



In the United States, chiefly owing to the zealous labours of 

 Sullivant, the knowledge of the productions of the parts investi- 

 gated by him and his coadjutors has been greatly increased ; but 

 the country is so extensive, and there remains such an unex- 

 plored region in the south, where the northern forms become 

 exchanged for those of tropical regions, which may probably be 

 better observed there than anywhere else, that it is to be expected 

 that great additions have yet to be made before the Bryology of 

 the United States is approximately exhausted. Besides the spe- 

 cies actually collected during the survey, there have been added 

 a few others, either overlooked or not before determined, mostly 

 collected by Drummond. 



The arrangement of the species contained in the following 

 enumeration is different from that employed in the ' Musci 

 Indici,' in which the pleurocarpous genera were arranged ap- 

 proximately in the order in which the substance of the leaves 

 became more and more indurated and obscure ; and the whole of 

 the Hypnoid mosses were divided into two sections by the 

 nerves of the leaves, those with a single nerve being considered 

 species of Hypnum, and those with two nerves or more were 

 referred to Bridel's Stereodon. But although this plan serves 

 very well to break up the tribe into two sections, there occur 

 here and there species which may sometimes answer to one and 

 sometimes to the requirements of the other section ; examples of 

 this occur in the species grouped in Idmnobiim, Schimper, in 

 Isothecium, and in Hylocomium, and are probably overlooked in 

 many species ; for in some the leaves of the main stem are faintly 



