1911-12.] BOTANICAL SOCIETY OF EDINBURGH 45 



At this stage the search gradually abated for nearly 

 thirty years longer until, in 1911, L. , p\iinilu r in (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 j)eculiarity 

 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 

 constitution 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 usuall}- narrowed and neare- 

 st raight. 



Orim/mia 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 

 frequently fastigiately branched ; leaves closely arranged 



