CRYPTOGAMIA. 373 



too few, and not strictly natural. Hedwig first 

 brought into notice the structure of the fringe, peri- 

 stomium, which in most mosses borders the orifice 

 of the capsule. This is either simple,y. 180 b, or 

 double,/. 213, 214, and consists either of separate 

 teeth, or of a plaited and jagged membrane. The 

 external fringe is mostly of the former kind, the 

 inner, when present, of the latter. The number of 

 teeth, remarkably constant in each genus and spe- 

 cies, is either four, eight, sixteen, thirty-two or sixty- 

 four. On these therefore Hedwig and his followers 

 have placed great dependence, only perhaps going 

 into too great refinements relative to the internal 

 fringe, which is more difficult to examine, and less 

 certain, than the outer. Their great error has been 

 laying down certain principles as absolute in form- 

 ing genera, without observing whether all such ge- 

 nera were natural. Such mistakes are very ex- 

 cusable in persons not conversant with botany on a 

 general scale, and whose minute and indefatigable 

 attention to the detail of their subject, more than 

 compensates the want of what is easily supplied by 

 more experienced systematics. Thus Barbula of 

 Hedwig is separated from Tortilla, Engl. Bot> 

 t. 1663, and Fissidens from Dicrartum, t. 1272, 

 1273, on account of a difference of form or situa- 

 tion in the barren flowers, which is evidently of no 

 moment, and merely divides genera that ought to be 

 united. The same may be said of genera founded 



