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 good a claim to a situation among the Endocarpa as among the 
Verrucarice. 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 arc 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 33r. 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.fusceilus 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 dili'crenc< 8; 
n 'I 3. Lichen 
