ON THE CRYPTOGAMIC BOTANY. XXV11 



high precipitous rocks, this spot cannot be reckoned as forming an 

 exception to the fact stated above. 



6th. When it is stated, besides, that there are distinct evidences, in 

 the majority of cases, of glacial action high up on the sides of such 

 ravines, but few or none near their base, the conclusion to which the 

 reader's attention is called becomes evident, viz. that such hollows 

 were protected during the period of the glacial drift by solid masses 

 of ice or glaciers, and that such plants (or their spores) as nourished 

 previous to this epoch were not destroyed, but allowed to remain 

 in statu quo. 



- Still referring to Ben Lawers, all the rare alpine mosses without 

 exception are found in the ravine, or on its lower slopes, which is 

 situated between the mountain and Craig-na-Gour on the west. It 

 is notable also that the truly alpine forms found in this ravine bear 

 a close resemblance to those corresponding to them from the Dovre- 

 feldt Mountains in Norway, so much so indeed that it is scarcely 

 possible to distinguish at sight whether any particular specimen is 

 Norwegian or Scottish. This fact surprised me more particularly 

 with reference to samples of Dicranum arcticum, Timmia Norvegica, 

 and the alpine states of Didymodon rubellus and Grimmia apocarpa. 

 I leave the reader's imagination to weave a theory, slender, yet I think 

 tenable, as to the disposition of the surface of the earth in Northern 

 Europe previous to the glacial epoch. My present limits will not 

 permit me to enlarge further in this direction, although much more 

 might be said on certain curious yet close affinities between the 

 vegetation of distant regions of Northern Europe. 



Peculiarities of Plant Distribution in the West of Scotland. 



What strikes a stranger most on oar western mountains is the 

 unusual prevalence, and, accordingly, luxuriance of species of the 

 genus Campylopus. Within a circle of a radius of 5 or 6 miles from 

 Ben Voirlich by Loch Lomond all the Scotch Campylopi, with one 

 or two exceptions, may be found, and much the larger proportion of 

 species of the nearly allied genera Dicranum and Dicrqnodontium. 

 These mosses give, indeed, a peculiar aspect to the vegetation of these 

 mountains, and they were, besides, the first to give a stimulus to the 

 study of Bryology in the West. In a short period no fewer than six 

 additions in these genera were made to the British Lichen Flora. 

 Now reckoning Ben Voirlich as the centre of spread, it is noticeable 

 that in a western direction the prevalence and luxuriance are 

 increased, while the number of species is diminished, until on or near 

 the sea-board the eye is attracted and ultimately wearied by extended 

 patches consisting almost entirely of C. longipilus. In the Western 

 Islands C. densus is the prevailing species, where it is found in 

 extended masses fruiting freely, while in the Outer Hebrides is found 

 the largest and most luxurious species of all, C. Shaivii. In an easterly 



