380 



MUSCI. 



great number of species that remain to be found, when 

 I mention, that the whole of the Hill collection was formed 

 between the 8th of October, and the 20th of November : and 

 that the most interesting portions of the hills to the Eastward 

 of the route mentioned were not visited. 



I know no arrangements of the genera, except the artificial 

 one employed by Dr. Hooker, and the artificial and natural 

 ones of Bridel, as given in his Bryologia Universalis. Mr. 

 Brown begins his account of the Melville Island Mosses with 

 Polytrichum. No very satisfactory ordination of all the ge- 

 nera has, I believe, as yet been given ; nor will it be, until 

 additional characters have been discovered. At the same time, 

 I think, that several types of organization exist, and that in 

 the larger groups of these, every gradation of development, 

 at least so far as the peristome is concerned, may be ob- 

 served. 



Sphagnum approaches, in some points, to Hepaticce, but I 

 doubt the correctness of its being stated to be evaginulate. 

 I have not been able to examine its fruits at different periods, 

 but it appears to me that the only difference between it and 

 the usual form, exists in the cohesion of the true apex of the 

 seta, with the interior of the vaginula. 



Polytrichum, in the structure and origin of its peristome, 

 has nothing in common with the usual form of mosses, in 

 which both peristomes originate from the inner membrane. 

 In the genus alluded to, and in one or two allied genera, it 

 is an extension of the outer wall of the capsule, shewing usu- 

 ally no indications of composition, and is probably analogus 

 to the annulus of the more developed genera of the order. 

 Its processes too are liable to vary in number, and they are 

 in some species much increased beyond the number 32, which 

 is the maximum number of a single peristome of the usual 

 structure, in which likewise no instance occurs of less than 

 16; for although Tetraphis has only four, and one or two 

 genera only eight teeth, the composition, as indicated by lon- 

 gitudinal lines ; is in all such 32. The smallest number, J 6, 



