242 PLAGIOTHECIUM MULLERIANUM IN BRITAIN. 



British Museum collection, its identity, as well as that of the 

 two earlier Scotch specimens, was at once established beyond 

 doubt. "'^ 



The addition of P. Milllerlanum to our list of recognized British 

 mosses is in itself of some interest, as the plant, a high alpine one, 

 is rare upon the continent. It has, moreover, certainly been mis- 

 understood hitherto ; Kindberg, for instance, makes it a variety of 

 P. 7iitidulum {= P. pulcliellum var. nitldulum), an arrangement 

 quite inconsistent with the actual facts; and I have received 

 specimens, named P. MilUerianimi on very good authority, from 

 North America, which proved to be autoicous and to belong to 

 P. pulchcllum. And as most of the works accessible to the 

 ordinary student give inadequate and even misleading descriptions 

 of the species, I have thought a full description would not be 

 without value. 



As far as I am aware, P. Mailer ianiim has only twice been 

 figured, by Husnot, in the Muscolo(jLa Gallica (Tab. c), and by 

 SuUivant (Icon. Muse, Suppl., Tab. 66). The former does not give 

 sufficient details to be of service in distinguishing the plant from 

 the allied species, and the latter, while giving an excellent figure, 

 is a scarce and highly expensive work, and one to which few 

 students could obtain access. It has seemed desirable, therefore, 

 to give a figure of the plant, which will, I believe, assist in rendering 

 its identification fairly easy. 



The only British species of Plagiothecium with which P. M'ld- 

 lerianum is liable to be confused are P. Borrerianiuii Spr.f and 

 P. pulchelliwi var. nitidulum Husn. (The continental P. inliferum 

 B. & S. is easily distinguished by the recurved leaf-margin, the 

 longer subfiliform acumen, and enlarged cells at the basal angles.) 

 P. Borrerianum usually grows in neater dense tufts, with very little 

 variation (in the same tuft) in the size of the leaves or branches. 

 The leaves are usually, though by no means always, decurved at the 

 tips, principally at the apex of the branches, which then present a 

 somewhat convex appearance from above. The acumen of the 

 leaves is almost always, perhaps invariably, more or less denticulate. 

 In P. MallenaniDii the habit of growth is much more irregular and 

 straggling, the branching irregular, and the branches themselves of 

 very different degrees of robustness. Schimper describes the plant 

 as minute, hardly larger than P. nitidulum, and most authors follow 

 him in this comparison. Limpricht, for example, whose diagnosis 

 is by far the fullest and most descriptive that I have seen, remarks 

 of it: "not distinguishable from P. pulchellum in size." This 



* I subsequently ascertained that a specimen of P. MUllerianum, labelled 

 " Ben Wyvis, Eoss-shire, Aug. 1867, A. McKinlay," exists in Schimper's 

 Herbarium at Kew ; I have not examined it, but there can be no doubt that 

 this is the same plant as that sent mo by Mr. Murray, and that its identification 

 as P. MUllerianum originally was by Schimper himself. It is remarkable that 

 uuder these circumstances it should have remained so long without recognition 

 as a British species. 



t The subsequent remarks apply equally to P. elejans (Hook.\ whether or 

 not that is identical with P. Borrerianum, 



