ORTHOTRICHUM. 249 



differing little from one another, yet sufficiently to render it very difficult in a 

 diagnosis to comprehend all except by the employment of very indefinite terms. It is 

 perfectly distinct from 0. cupulatum and 0. anomalum in the superficial stomata, 

 while in habit often very similar ; it rarely however, if ever, has the 16 distinct ribs of 

 the former, while O. aiwmalum and its var. saxatile have the capsule more exserted, 

 the former, too, usually showing 16, and the latter more marked ribs. From all the 

 other British species it is easily distinguished either by its rupestral habit or the non- 

 reflexed peristome. 



The var. Sturmii is a. very unsatisfactory plant. The slightness of its claims to 

 independence is best shown by the way in which characters once held distinctive have 

 been dropped and new ones again and again brought forward, only to meet the same 

 fate. All the secondary characters given above have at one time or another been 

 claimed as specific characters, and have one by one been rejected, and all that can be 

 said is that they are more frequently found in plants with the short-necked capsule of 

 var. Sturmii than in those of typical tupestre. Intermediate forms of capsule are 

 also far from rare. 



The var. Franzonianum too is perhaps only an arboreal form of this species ; 

 it has, however, a different facies, and the difference of habitat is certainly a striking 

 one in so decidedly a rupestral plant as the present. My plants have a paler, rather 

 inflated calyptra, and in these as well as in American plants I possess of this variety, 

 the stomata occur on the upper part of the capsule, sometimes indeed very near the 

 mouth. 



Two other varieties are described as British — var. rupincola Hiibn. , a short, 

 compact form, and var. Sehlmeyeri, a taller, looser plant, but neither appears of great 

 importance. 



O. rupestre prefers dry rocks, and is found most abundantly on stone walls by 

 roadsides in mountainous regions. 



B. CUPULATA. 



2. Orthotrichum anomalum Hedw. (Tab. XXXIV L.). 



In close cushions, rather rigid and fragile, dark olive green or 

 brown, £-1 inch high. Leaves erecto-patent, when dry straight 

 and closely imbricated, widely ovate-lanceolate, somewhat taper- 

 ing but suddenly and rather broadly pointed ; margin recurved, 

 sometimes widely so ; nerve strong, ceasing below the point ; 

 basal cells rectangular, pellucid, upper hexagonal-rounded, rather 

 thin-walled or incrassate, usually arranged in very regular longi- 

 tudinal rows : always in a single layer ; papillae small, simple. 

 Capsule usually very slightly exserted above the perichastial 

 bracts, rather large, pale reddish brown with 16 brighter coloured 

 ribs, 8 principal ones extending the length of the capsule, and 8 

 intermediate less strong and often shorter ones ; the 8 primary 

 ribs composed of 2-3 longitudinal rows of cells with thick longi- 

 tudinal and thin cross walls, the 8 secondary ones narrower, some- 

 times very inconspicuous. Capsule widely cylindric or oval- 

 cylindric, almost exactly cylindric when dry and empty, tapering 

 quickly into the conical neck which gradually passes into the 

 rather long seta. Stomata immersed, guard-cells about half 

 covered by the superficial cells. Calyptra yellowish green, rarely 



