AMBLYSTEGIUM. 445 



6. Amblystegium fluviatile B. & S. (Hypnum fluviatile 

 Sw.) (Tab. LVI. D.). 



Allied to the preceding species ; differs in the longer, almost 

 simple divisions of the stem, with few, hardly pinnate, parallel 

 branches, in softer, more floating and elongated tufts, deep green, 

 often blackish. Leaves less spreading, more erect when dry , and 

 often, in the more dense-leaved forms, somewhat spirally 

 imbricated ; narrower, oval-oblong or oblong-lanceolate , not 

 dilated at the base, and less distinctly decurrent ; much more 

 gradually tapering to a much shorter, wider point, muticous or 

 almost obtuse, not narrow nor acute ; margin quite entire or very 

 faintly sinuolate ; nerve very stout and thick, hardly narrowing 

 in the point, and usually reaching distinctly to the apex, though 

 often becoming confused with the somewhat obscure apical 

 areolation. Cells as in the last, or slightly larger and less opaque ; 

 at base rather more distinctly rectangular, pellucid or opaque, 

 often orange, strongly incrassate, not forming distinct auricles. 

 Capsule longer, narrowly cylindrical, suberect, slightly, not 

 strongly arcuate, much constricted below the mouth, often more 

 strongly in front so that the mouth is incurved, darker in colour 

 and of thicker texture. Autoicous. 



Hab. Stones in mountain streams ; rather rare. Fr. summer. 



A. fluviatile is in general easily known from the preceding species by the characters 

 italicised above and pointed out under the above plant ; the difference in the leaves 

 will perhaps be best realised by a comparison of the figures. According to Boulay, 

 Husnot, etc., intermediate forms are frequently found, and the former author even 

 considers it a sub-species of A. irriguum. I have not been able to find any constant 

 differences in areolation, such as are sometimes described, between the two, and the 

 less rigid texture ascribed to A. fluviatile, though usual, does not appear to be a 

 constant character ; on the other hand the characters derived from the leaf-form and 

 nerve are well marked in all the British specimens I have examined, and in all 

 probability the intermediate forms mentioned above are practically confined to 

 continental Europe ; the student will not, I believe, find any great difficulty in regard 

 to our British plants. 



The present species is usually found in more rapid streams than the last, and is 

 more distinctly aquatic ; much of the difference in its habit and branching is doubt- 

 less owing to this fact. 



7- Amblystegium filicinum De Not. (Hypnum filicinum 

 L., Schp. Syn. et plur. auct.) (Tab. LVI. F.). 



Very variable in habit, the stems typically erect or ascending, 

 rigid, divided, somewhat regularly but not complanately pinnate ; 

 forming loose or dense rather rigid tufts of a bright or golden 

 green colour. Stems usually densely tomentose with brown 

 radicles for the greater part of their length, especially in the 



