16 GYMNOSTOMI. [ Gymnostomum. 



in a fresh state ; such as G. microstomum, G. fasciculare, G. trun- 

 catulum, and especially in G. Griffithianum, in which this mem- 

 brane is not unfrequently entire ; without, however, in the least 

 considering it to invalidate the character of the genus. Nay, we 

 are disposed to go further, and to believe, from subsequent obser- 

 vations of ourselves and others, that such a membrane in an early 

 state of the plant may be found in all of the genus. As to the ex- 

 act origin of this membrane, whether it is attached as a covering 

 to the columella, or whether it springs from the very inner mem- 

 brane or edge of the mouth of the capsule, as the teeth in Weissia 

 for instance, or Tortula, are found to do, w.e confess we have 

 not been able entirely to satisfy ourselves. Whilst, however, it 

 constitutes nothing but this horizontal membrane, disappearing 

 partly or entirely after the fall of the operculum, we consider it of 

 no importance in the generic character ; hence we can by no 

 means consent to adopt the GEdipodium of Schwaegrichen, how- 

 ever different that plant may be in habit from the other Gymno- 

 stoma, nor the Hymenostomum of our illustrious countryman 

 Brown, (and adopted by Nees and Hornschuck), and which quite 

 agrees in habit with some well kno\vn Gymnostoma. 



Sometimes an oral membrane in the Mosses destitute of real 

 teeth, takes another character ; it forms an erect annulus after the 

 fall of the operculum, sometimes having regular plicae and itself 

 of great length, as in Diphyscium ; at another time breaking into 

 a definite number of teeth,* and that number corresponding with 

 the number we find to be so common in the Mosses furnished 

 with real teeth, as in our Weissia trichodes ; we then consider 

 that such mosses should be removed from Gymnostomum. 



A third kind of membrane at the mouth of the capsule remains 

 to be noticed, which is that, where it forms *& short upright an- 

 nulus more or less jagged at the margin, but without any regu- 



* An appearance of this kind has indeed been described and figured by Dr. 

 Hooker in Leptostomum erectum, Br. Muse. Ex. t. 169. ; and Dr. Greville and 

 Mr. Arnott in their Tent. Meth. Muse. 2d. Mem. state that they have seen a 

 similar division of the membrane to occur in Gymn. microstomum. If these 

 authors have not been deceived, then they may afford some further character for 

 distinguishing these plants from Gymnostomum than has yet been known. 



