POLYTRICHACE^E.J 44 [Polytrichum. 



divergent, not dilated at base, elongated, pale green, pellucid, with larger 

 areolation ; nerve broader, margin more or less distinctly subserrated. 



HAB. Ben Nevis (McKinlay 1863) ! near Bangor, N. Wales (J. Griffiths 



1879) ! ! 



I am indebted to the kindness of Mr. Hobkirk for this very striking 

 variety, only found in the barren state. 



3. POLYTRICHUM DILLEN. 



(Cat. pi. giss. 211 (1718).) 



Plants short and simple, or tall, showy and branched, innovating 

 from radical protonema, or subterranean stolons, or from middle of 

 stem. Leaves from a membranous, sheathing base, rigid, coriaceous, 

 scarce altered by drying, nerve broad, covered with very numerous 

 erect lamellae, margin spinoso-serrate. Calyptra dimidiate, with straight 

 defluent tomentum, covering all or most of capsule. Capsule erect 

 or cernuous, terete and cylindraceous, or prismatic or cuboid, and 4, 

 rarely 5 6 angled, tapering to a neck or with a small discoid or 

 subglobose hypophysis. Lid convex, apiculate or with a straight 

 beak. Teeth 32 or 64, adhering at apex to the papery epiphragm. 



An extensive genus scattered over the whole world and exhibiting 

 great diversity in the size of the individuals, some of the species forming 

 small groups of closely allied forms. Above 100 species belong to the 

 sections with rounded fruit (commonly combined into the genus Pogonatum] 

 and about 30 to that of Eupolytrichum. The derivation is from TroAvs many, 

 Opig hair. 



CLAVIS TO THE SPECIES. 



Capsules rounded. 



Leaves short, broadly lanceolate, subinvolute at margin. 



Leaves obtusely toothed. Capsule subglobose. Columella cylindric. 



subrutundutn. 

 Leaves sharply serrate. Capsule longish oval. Columella 4-winged. 



aloides. 

 Leaves longer, narrowly lanceolate, acute. 



Capsule subcylindric, erect, terete, papillose. urnigeruin. 



Capsule oblong, tumid, somewhat inclined, smooth. alpinum. 



Capsules angular. 



Leaves entire with an inflexed margin. 



Leaves obtuse at apex. sixangularc. 



Leaves aristate at apex. 



Arista short, smooth, coloured ; stems short, leaves spreading, recurved ; 



capsule square, prismatic. junipcrinnni. 



Arista the same; stem tall, leaves erecto-patent, straight; capsule small, 



cuboid. strictum. 



Arista longer, rough, hyaline. pilifcrwn. 



Leaves sharply serrated, plane, acuminate. 



Capsule ovate, obscurely angled, lid rostrate ; leaves short. gracile. 



Capsule oblong, 4 6 angled, leptodermous ; lid conical, pointed. 



attenuatum. 



Capsule cubic, acutely 4-angled, pachydermous, with a distinct hypophysis ; 

 lid conico.rostellate commune. 



