four new British Lichens. 91 



but also an interesting species, as it shows how nature, by insen- 

 sible gradations, unites even those tribes that are most different 

 from each other; its thick crust and immersed thalami, not punc- 

 tured at the summit, leaving it almost doubtful whether it has not 

 as s;ood a claim to a situation among the Endocarpa as among the 

 VerrucaricB. I should, however, certainly place it with the latter; 

 but even here I must be allowed again to observe, that Dr. Acha- 

 rius has introduced several plants which, in my opinion, belonged 

 far more properly to the Fungi ; and 1 trust that these remarks 

 will not be considered as made with a view to detract from the 

 character of that excellent botanist, of whose merits I am fully 

 sensible ; for even he has entertained doubts upon the subject : 

 and it may be hoped, that in the new edition now preparing of 

 his Lichenographia, he will reject all those species that are not 

 provided with a real crust, separable, or at least easily distin- 

 guishable by the eye from the substances to which they are 

 attached. From Dr. Acharius's description, it might be supposed 

 that the present species is the same as his L.griseus: but it is to 

 be observed, that he takes up that plant on the authority of Dr. 

 Persoon, who, in the place referred to, says that the crust is green 

 within, and turns to that colour also, if moistened ; in both which 

 points it entirely disagrees. There is a Lichen found occasionally 

 on old oaks, and not at present, 1 believe, noticed by any author, 

 from which it seems to me more probable that L.fiisccllus is not 

 specifically distinct. They agree in colour and appearance, but 

 differ in the thalami of that which grows on wood not being of so 

 regular a form as those of the other, as well as in its crust being 

 far less thick : and hence I have not ventured upon making them 

 the same; for in plants themselves so minute we cannot but ex- 

 pect the species to be separated by minute differences. 



n 2 3. Lichen 



