Mosses — Grimmia and Schistidium. 



107 



columella adhering to the lid, and all its capsules sub-sessile and 

 immersed. 



Grimmia orbicularis, of which we give a magnified illus- 

 tration, with stem leaves very highly magnified, grows on 

 calcareous rocks, with densely tufted stems, and crowded 



oblong - lanceolate 

 leaves, having long 

 diaphanous points, 

 and small dot-like 

 cellules, in straight 

 longitudinal lines. 

 These cellules are, 

 however, enlarged 

 towards the basal 

 margins, and as 

 they descend the 

 stem the leaves are 

 less crowded, di- 

 minish in size, be- 



Grimmia orbicularis. COme destitute of 



the bristle, and are even somewhat obtuse pointed. 



The capsule is roundish, on a pale yellow curved fruit-stalk ; 

 the capsule itself as it ripens passes from pale yellow to bright 

 red, is smooth and glassy while recent, but obscurely striated 

 or ribbed when dry ; the walls of a rather thin or semi-opaque 

 texture, with a narrow annulus and a very short mammillate, 

 but never rostellate lid. The teeth of the peristome rather 

 short and broad, trifid, sometimes quadrifid at the apex, semi- 

 opaque, of a pale red, rather distantly marked externally with 

 transverse bars, and much perforated or crib-rose towards the 

 base ; they are erect or converging when dry. The calyptra 

 is dimidiate and soon falls away. 



Though Grimmia orbicularis ripens its fruit at an earlier 

 period, it sometimes, as we have before said, grows intermixed 

 in the same tuft with a more common species, Grimmia pulvi- 

 nata, or the grey -cushioned Gh'immia, which is commonly found 

 on walls and roofs, as well as upon rocks ; it, too, grows in 

 densely tufted round patches, with branching stems, from half 

 an inch to an inch in height, and with leaves very much resem- 

 bling those of the preceding species, being elliptic-lanceolate, 

 suddenly attenuated and piliferous, terminating in long white 

 hair-points, but the leaf is broader than in orbicularis ; cari- 

 nate, with a somewhat stronger nerve, which vanishes below 

 the hair-points, and though both are hoary from their white 

 terminal points, the foliage of pulvinata is of a more yellowish 

 green; that of orbicidaris has a bluer hue, and more dingy 

 appearance. 



