DITRICHUM. 57 



/Ls. squarrose, suddenly contracted from a broad sheathing base i. tenuifolium 



\ Ls. erecto-patent or secund 2 



/Stem tall, flexuose ; ls. very long, usually falcate ; cells shortly oval. ..5. flexicaule 



\Stem short, straight; ls. patent or subsecund -. 3 



/Lid conic, obtuse; capsule dark red ; dioicous .j. homomallum 



J \Lid rostellate ; capsule pale or golden brown 4 



/Nerve slightly excurrent, toothed at apex ; dioicous 2. tortile 



4 \Nerve longly excurrent, entire (or nearly so) ; paroicous 4. subulatum 



1. Ditrichum tenuifolium Lindb. (Trichostomum tenuifolium 

 Schrad. ; Trichodon cylindricus Schp., Syn.) (Tab. XII. H.) 



In yellowish green tufts, or gregarious ; stems short, usually 

 simple. Leaves flexuose, squarrose from an oblong sheathing 

 base, suddenly narrowed to a fine, almost setaceous subula, the 

 greater part formed of the nerve, irregularly and closely 

 denticulate and rough with the projecting transverse walls of the 

 cells; margin plane; areolation at base narrowly rectangular, 

 long, almost hyaline ; shorter above, in the subula irregularly 

 quadrate, hardly distinct from the cells of the nerve, obscure. 

 Seta pale red, long ; capsule erect or slightly inclined, straight or 

 faintly curved, narrowly cylindric, smooth ; lid obtusely conical ; 

 annulus broad, of two or three rows of cells ; peristome teeth 

 pale red, papillose, the divisions occasionally slightly united 

 towards the base. Dioicous. Male plants more slender, in 

 separate tufts, bracts subulate, concave. 



Hab. Wet sandy ground in waste places, rare. Fr. summer, but rarely fertile. 



The structure of the peristome, having the divisions of the teeth occasionally 

 united a little above the base, and the broader annulus of several rows of cells, are 

 somewhat characteristic of the genus Ceratodon ; but the form of the leaves and the 

 smooth cylindrical capsule seem to justify its inclusion in the present genus ; the 

 squarrose leaves, suddenly narrowed from the broad sheathing base and very rough in 

 the upper part will serve to separate it from the others of the genus ; and its general 

 appearance is indeed more that of Dicranella Grevilleana and D. Schreberi, to which 

 in fact it bears a close resemblance in the leaves ; in the former of these two species 

 however the leaves are entire or nearly so, and in the latter the subula though 

 frequently toothed above, is usually so on the margin alone, not nodulose and papillose 

 all round as in the plant under consideration, nor are the cells in the upper part so 

 obscure. The two plants however, in the barren state can often be separated only by 

 very careful examination. 



D. subulatum has the leaves erecto-patent when moist, and the subula only faintly 

 denticulate. 



2. Ditrichum tortile Hampe (Trichostomum tortile Schrad. ; 

 Leptotrichum tortile Hampe, Schp. Syn.) (Tab. XII. I.) 



Tufted, pale green, stems simple or nearly so, short. Leaves 

 short, patent or turned to one side, slightly curved, gradually 

 narrowed from a narrowly ovate or oval-triangular base to a 



