172 ANNALS OF SCOTTISH NATURAL HISTORY 



rudimentary propagula ; accordingly the minute structure of 

 the leaf requires examination for adequate determination. 



Along the main road at Arisaig grows a Grimmia on 

 stones which, in wet weather, has a peculiar glossy or silky 

 sheen, such as I have not seen in any other species of this 

 perplexing genus. The flat tufts are often extended con- 

 tinuously from two to six inches, but the strange 

 peculiarity about it is its rapidity of growth. I have 

 watched a tuft of Grimmia Stirtoni (Sch.), near Killin, from 

 year to year for the purpose of getting fruit, showing 

 scarcely any difference in the size of the button-like patches. 

 On the contrary, this moss, during three months, often 

 extended from two inches to nearly four, and what is more, 

 minute new patches became quickly visible in the near 

 neighbourhood. Moreover, in 1904 this moss could be 

 detected for not more than half a mile, while in 1906 it 

 could be traced for nearly double that distance. It never 

 fruits. By what means was it propagated so quickly ? 

 This puzzled me, until in the beginning of September, 

 during rainy weather, propagula were seen in abundance at 

 the apices of stems, and generally attached to leaves near 

 their bases as well as to the stems themselves. These 

 propagula are quite unique in character. They are globular, 

 yellow, then reddish-brown, simple, or at times I -septate, 

 with granular contents, in clusters or in short chains, and large, 

 .O3-.O38 mm. diam. A question arises whence the origin of 

 this moss, or, rather, whence the origin of these germinat- 

 ing cells. This question is rendered more difficult of 

 solution from the fact that the moss grows nowhere else in 

 the district, and I have not observed it in any of my 

 rambles elsewhere. 



Grimmia polita. Tufts extended, of a yellowish green 

 colour, stems strong, simple, or not infrequently somewhat 

 fastigiately branched above : leaf a little crisped when dry, 

 laxly spreading when wet, or cohering in little bundles during 

 wet weather, ovate lanceolate acuminate, terminating in a 

 long, nearly smooth hair; nerve strong, .065 mm. broad 

 near base, scarcely narrowing upwards for more than the 

 lower half, turning red, of rather dense structure within, 

 but on the very prominent convex back a row of close cells, 



