GRIMMIA. 145 



19. Grimmia commutata Hiibn. (G. ovata W. & M., 



Braithw. Br. M. Fl.) (Tab. XXIII. A.). 



Taller and more robust than the last, in larger less compact 

 cushions, i-if inches high, dull green or blackish. Leaves less 

 crowded, less regularly appressed when dry, larger and longer, 

 i-ij lines long, more uniform throughout the stem, very concave, 

 from a short, very broad sheathing base, lanceolate, ending in a 

 rather long, stout, faintly denticulate hair; nerve distinct, rather 

 narrow, obscure above ; margins plane, erect or slightly incurved, 

 not thickened, basal cells resembling the last, but with a much 

 wider band of marginal hyaline cells, in 5-10 rows ; very quickly 

 becoming sinuose-quadrate, above rounded-quadrate, incrassate, 

 very obscure, bi-stratose. Dioicous. Capsule on a pale seta, 

 exserted, oval, brown, smooth, contracted at mouth ; calyptra 

 cucullate, large ; lid with a longer oblique beak ; peristome teeth 

 divided to the middle and perforate. 



Hab. Siliceous rocks. Rare. Fr. spring. 



This is a coarser, more robust plant than the last, more hoary with the hair- 

 points, and especially distinct in the inflorescence. The character drawn from the 

 calyptra is rather misleading, since, according to Boulay, the base is sometimes 3-4 

 lobed, while in G. ovata it is not uncommon to find it sub-cucullate, deeply cleft on 

 one side aud oblique, and only very faintly lobed otherwise. G. montana and G. 

 alpcstris differ in the shorter basal cells and less concave leaves. 



20. Grimmia montana B. & S. (Tab. XXIII. B.). 



In low compact cushions, scarcely an inch high, dark green, 

 or hoary with the hair-points of the leaves ; leaves erecto-patent, 

 erect when dry, resembling those of G. ovata in shape, lanceolate 

 from a broader base, short (f-line long), margins plane ; hair- 

 point fully as long as the leaf in the uppermost leaves of the stem, 

 denticulate, wide at base and decurrent, nerve distinct ; basal 

 cells almost uniform, resembling those of G. pulvinata, 

 rectangular, hyaline, short (1^-2 times as long as broad), with 

 rather thin but firm, not sinuose, walls, those nearest the nerve a 

 little narrower and longer; above quickly becoming small, 

 chlorophyllose, quadrate, faintly sinuose, in upper half small, 

 roundish-quadrate, obscure, incrassate. Dioicous ; seta short, 

 pale ; calyptra cucullate, large ; capsule shortly oval or oval- 

 oblong, smooth, reddish brown ; lid rostrate, ]A, length of capsule. 

 Peristome teeth pale, narrow, irregularly cleft. 



Hab. Siliceous and calcareous rocks at low elevations. Rare. In fruit, Fingle 

 Bridge, Devon. Fr. spring. 



