440 Rev. W. A. Leighton on the Lichens of Spitzbergen. 
navia, with the single exception of Usnea sulphurea, which occurs 
in Arctic America, and from which a connexion between the 
vegetations of the two regions may be conjectured. | 
Nevertheless there are marked differences, the chief of which 
is the absence or very partial occurrence of the larger fruticulose 
and foliaceous lichens. Those which do occur assume an ab- 
normal aspect of dense cespitose pulvinuli, without apothecia. 
The absence of trees and wood causes the corticolar species to 
be found in a masked form on mosses, old cottages, crosses, &c., 
in company with many which ordinarily grow on mosses and 
rocks. 
The lichens which, in northern regions, usually cover the 
marine rocks are, through the intense severity of the climate, 
altogether absent or of very rare occurrence. . 
A comparison of the number of the Spitzbergen lichens with 
those of Arctic Scandinavia shows that the former are very 
deficient. But, on the other hand, the Spitzbergen lichens far 
exceed in number and abundance those which have been de- 
tected in analogous Antarctic regions. 
Malmgren has collected in Spitzbergen lichens 2300 feet 
above the level of the sea, from which he deduces that, contrary 
to former opinion, the line of perpetual snow does not here 
descend to the sea; but, on the contrary, that wherever in these 
lands there are localities which at times are denuded of snow 
and ice, there lichens will fix themselves and flourish. He also 
shows that, as in flowering plants, so also in lichens, there is a 
decided difference between those of the northern and western 
sides and those of the other sides—doubtless arising from the 
different geological formations. 
With much satisfaction we observe that the learned author 
has overcome his prejudice against the application of chemical 
tests in lichens, and has made ample use of them with ve 
satisfactory results. He, however, still appears to labour under 
a misapprehension that the advocates of chemical tests wish to 
inculcate that species may be distinguished by chemical means 
alone (“hac sola nota”). All that has ever been ascribed to 
them is that they are most useful and indispensable aids, as 
affording confirmatory characters and in discriminating doubtful 
or externally allied species. In the Cladonize he has almost 
uniformly confirmed the results of our own examination of this 
tribe (see Aun. & Mag. Nat. Hist. Nov. 1866 and Feb. 1867). 
But it may he well here to correct a doubt which seems to exist, 
in consequence of the chemical test producing in certain species 
a slight degree of fuscescence only, by explaining that when the: 
proper reaction takes place, it does so instantly, and that that 
fuscescence which is in some instances observable is not to be 
