4Q2 CRYPTOGAMIA. 



has been laying down certain principles as 

 absolute in forming genera, without ob- 

 serving whether all such genera were na- 

 tural. Such mistakes are very excusable 

 in persons not conversant with botany on 

 a general scale, and whose minute and in- 

 defatigable attention to the detail of their 

 subject, more than compensates the want 

 of what is easily supplied by more experi- 

 enced systematics. Thus Barbula of Hed- 

 wig is separated from Tortilla, Engl. Bot. 

 h 1 663, and Fissidens from Dicranum, 

 i. 1272, 1273, on account of a difference 

 of form or situation 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 on the union of the stamens and 

 pistils in one flower. On this subject I 

 have been more diffuse in a paper on 

 Mnium, in IV: of Linn. Soc. v. 7, 234, 

 to which I beg leave to refer those who 

 are desirous to study it further. Various 

 and abundant specimens of this tribe of 

 plants, showing the various structure of 

 v ' the fringe, lid and other parts, may be 



