go THE SCOTTISH BOTANICAL REVIEW 



years longer until, in 1911, L. puviiluin (Michx.), the moss to 

 which attention had been drawn fifty years previously by 

 Professor Schimper, was found near Gairloch, growing on the 

 debris of the Torridon Rock. 



I have carefully compared genuine specimens of this moss 

 from Dr. Braithwaite, who got them from Mrs. Britton, keeper 

 of the Moss Herbarium in Bronx Park, New York, and the 

 Scottish and American specimens agree in every particular. 



Whilst working amongst the Torridon Rock what struck 

 me as very peculiar is the fact that, in spite of its hardness, 

 it is easily disintegrated by the rootlets of slender mosses. 

 Many such, chiefly species of the genus Grimmia, are found 

 growing on large exposed masses of this rock and mostly 

 in saucer-like depressions. On detaching these tufts they 

 appear as if they had been reared in loose sand, whilst a 

 corresponding cavity in the rock is revealed. I may return 

 to this subject on another occasion. Another peculiarity 

 presented is the deep dark-green colour assumed by mosses 

 growing on it, while the same mosses growing on other rocks 

 usually exhibit a greyish appearance more or less deep. 

 That this prevailing deep green is not of the same constitu- 

 tion throughout may be inferred from the fact, that in some 

 instances it changes, in the course of two or three weeks, 

 to a deep coppery hue throughout the entire plant, in 

 others it slowly turns to a dingy yellowish-green, while in 

 the majority of cases the colour remains nearly unchanged 

 for many months. 



An instance of the first of these changes in colour is the 

 following which, besides, is remarkable otherwise, owing to 

 the peculiar shape of a proportion of the upper cells of the 

 leaf, viz. barrel-shaped, with lateral walls, convex and rugose, 

 while the ends are usually narrowed and nearly straight. 



Grimmia rubescens, sp. nov. — In small, dense, convex tufts 

 of a dark green above, rapidly changing throughout to a dark 

 copper colour, quite unlike the dingy grey usually assumed 

 by others of the same genus ; stems about an inch long 

 or less, simple or dichotomously divided, much less fre- 

 quently fastigiately branched ; leaves closely arranged around 

 stem, spreading slightly and straight when moistened, 

 narrowly ovate lanceolate, ending in a broad apex, latit. 



