218 



The Scottish Naturalist. 



the same time to endeavour to find more of the moss. I followed 

 his advice during several years, but without success. The matter 

 lay in abeyance — almost in oblivion — until three years ago ; when 

 Mr. G. Horn, of Glasgow, sent me a specimen from Glen Ogle 

 which served to recall all the circumstances of the case. 



An examination of the areolation under the microscope has 

 convinced me that the moss is undescribed, though having an 

 affinity to Gr. elongata. The reddish-brown colour of the bases 

 of the older leaves confirms me in this opinion, as the colour is 

 very peculiar, and is seen in very few Grimmioe. The following 

 may serve by way of diagnosis. 



Grimmia Rorni sp. n. — Densely caespitose, when freed from 

 earth dark or nearly black, slightly hoary on surface owing to the 

 presence of short colourless hairs on the upper leaves ; stems 

 sparsely dichotomous, slender, free of radicles ; leaves rigid, 

 appressed to stem and straight when dry, spreading slightly when 

 moistened, but remaining straight, shortly and broadly lanceolate 

 (measuring on an average 1*3 + '47 mm.), margin scarcely re- 

 flexed near base, plane above and very slightly thickened ; nerve 

 slightly hollow in front, hair-point nearly smooth, short, deciduous 

 and seen only on the leaves at the summit of the stems. 

 Areolation at centre of base smooth, cells long, narrowly rect- 

 angular, 35-50 by 6-9 ; at margins of base nearly square with 

 roundish angles, 18 by 16; cells beyond these smaller, shortly 

 oblong, not sinuous ; upper cells small, dense, and irregularly 

 quadrate. 



Hab. on bare rocks in Glen Ogle (G. Horn). The leaves of 

 Gr. elongata are not so broad, but they are nearly twice as long 

 as those of this moss. The sharply sinuous cells so abundantly 

 seen in Gr. elongata, and so characteristic of it, are absent from 

 G. Horni; and altogether the differences are such as to indicate 

 specific distinction. The moss can easily be discriminated in the 

 field, a characteristic on which Prof. Schimper laid great stress. 

 The areolation differs considerably from that of Gr. Stirtoni, to 

 which it bears, at first sight, some resemblance ; while the de- 

 lapsing stems suggest at first a dark stunted form of Gr. funa/is. 



While on this topic I may mention that the specimens of Gr. 

 elongata, found by the Rev. J. Fergusson, differ very considerably 

 from authentic specimens from Norway (at least as regards those 

 found in Glen Callater), in the shape of the leaf as well as in 



