440 Rev. W. A. Leightou on the Lichens of Spitzhergen. 



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 diflferences, 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 Spitzhergen lichens with 

 those of Arctic Scandinavia shows that the former are very 

 deficient. But, on the other hand, the Spitzhergen lichens far 

 exceed in number and abundance those which have been de- 

 tected in analogous Antarctic regions. 



Malmgren has collected in Spitzhergen 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 very 

 satisfactory results. He, however, stdl 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 Cladonise he has almost 

 uniformly confirmed the results of our own examination of this 

 tribe (see Ann. & Mag. Nat. Hist. Nov. 1866 and Feb. 1867). 

 But it may be 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 



