Fam. 10. GRIMMIACE^. 



Plants tufted in small cushions, or in large lax mats, the stems 

 repeatedly dichotomous. Leaves pluriseriate, ovato-lanceolate, dull 

 green, opake, lower cells hexagonal or linear, frequently with the inner 

 wall sinuate, upper minute quadrato-rotundate, highly chlorophyllose. 

 Capsule on a straight or arcuate seta, erect, usually equal. Calyptra 

 mitrasform, enclosing the whole or part of capsule, rarely cucullate, 

 smooth or sulcate, often pilose. Peristome rarely none, single or double, 

 teeth plane, rarely filiform. Male inil. gemmiform. Inhabiting rocks 

 and stones or the bark of trees. 



This great family, including about 700 species, falls naturally into two 

 groups, of which Grimmia and Orfhotnchum are the types ; and as in both 

 genera considerable uniformity exists in the leaves, we require to have good 

 fruiting specimens for their satisfactory determination, as the calyptra and 

 seta in Grimmia, and the peristome and stomata on the wall of the capsule in 

 Orthotyichum are of primary importance. 



The species of Grimmia have a distinctive aspect in their grey tufts, very 

 often hoary with the white hairpoints terminating the leaves, or they form 

 black fragile patches on the exposed rocks of the higher mountain regions. 

 I have followed C. Mueller, Mitten and Lindberg in uniting Rhacomitrium with 

 Grimmia, as the linear crenulate leaf-cells regarded as characteristic of the 

 former genus, will be found appearing in many species of the latter. 



Orthotrichum also has a peculiar habit which is soon recognized, 

 though the Schistidium section of Grimmia closely resembles it. The 

 stems are pulvinate or crowded into depressed tufts, dichotomously 

 fastigiate-branched, short and erect, or longer and decumbent or creep- 

 ing, as is more especially the case in the vast exotic genus Macromitrium 

 (which comprises one-third of the whole family), and also in Schlotheimia 

 and Drummondia. The leaves are often cirrhato-crispate when dry, 

 patent or squarrose when moist, hardly ever hoary at point, oblong- 

 lanceolate, entire and papillose, the vaginula ochreate and often pilose, the 

 calyptra mitraeform or subcylindric, longitudinally plicate, rarely smooth, the 

 capsule erect, immersed or somewhat exserted, with a tapering neck, costate 

 or striate ; peristome very rarely none, simple, of 8 bigeminate or 16 geminate 

 broadly lane, teeth, very often with an endostome of 8 or 16 cilia 

 alternating with them. The great variability of the peristome has struck all 

 writers, and shows how insufficient this organ is of itself to afford generic 

 characters. 



