148 GRIMMIACE/E. 



The broadly-pointed leaves, quite without hyaline points, with thickened margins, 

 distinguish this species from G. elongata, and indeed from all the species hitherto 

 described, G. patens differing widely in habit, in the leaves straight when dry, etc. ; 

 it differs from the next in the less obtuse, not cucullate, less solid and opaque leaves, 

 and is more like Rhacomitrium ellipticum, which however also has straighter leaves 

 when dry, and the areolation altogether different. 



25. Grimmia unicolor Hook. (Tab. XXIII. G.). 



Tall and robust, dull green, blackish below, 1-3 inches high, 

 in looser tufts, less coherent than the last. Leaves from an oblong 

 concave base narrowly linear or ligulate, obtuse and rounded at 

 apex with the margins incurved and cucullate, not hyaline-pointed, 

 nerve less prominent behind, flattened and somewhat indistinct, 

 margin plane ; basal cells thin-walled, rectangular, 2-4 times as 

 long as broad, the marginal slightly more hyaline and distinct ; 

 very quickly becoming short, incrassate, quadrate or rounded, not 

 sinuose, in 2 or 3 strata above and very obscure and opaque. 

 Capsule oblong, exserted on a rather long fruitstalk, erect or sub- 

 oblique, slightly contracted at the mouth ; lid long-beaked ; 

 calyptra mitriform or sub-cucullate. Dioicous. 



Hab. Alpine rocks ; very rare. Clova. Fr. winter. 



The leaves of this plant are quite different in the form of their apex from those 

 of any other Grimmia, and this, with the total absence of hair-point, abundantly 

 distinguishes it. It resembles G. patens in some respects, but the two-winged nerve 

 in that species is visible even with only a pocket lens, so that there need be no 

 confusion between the two. 



30. RHACOMITRIUM Brid. 



Plants with the stems usually elongated, dichotomously 

 branched, the branches often clothed with numerous short lateral 

 branchlets ; leaves like those of Grimmia, often hair-pointed, 

 cells strongly sinuose, the lower all elongated, narrow-linear and 

 nodulose, a very few at margin occasionally different. Seta erect ; 

 calyptra mitriform, longly subulate, often papillose, not plicate ; 

 capsule oval, oblong or cylindrical, smooth ; peristome as in 

 Grimmia, or with the teeth divided almost to base into two straight, 

 filiform branches. Dioicous. 



Although closely allied to Grimmia and more or less connected 

 with that genus by certain species, the present genus has a 

 distinct character of its own, and apart from the habit and mode 

 of growth, some of the structural characters given above are by 

 no means unimportant ; and the separation of the two genera 

 while, to say the least, permissible, is undoubtedly desirable from 



