ORTHOTRICHUM. 255 



hidden by the overlapping cells. Spores small, about 12 /*. 

 Autoicous. 



Hab. On rocks and tree-roots by water, in places at least partially submerged, 

 not common. Fr. summer. 



A distinct species, both in its habitat, and its dark colour, as well as in the obtuse 

 leaves and strongly ribbed capsule, markedly contracted below the mouth when dry. 

 From 0. affine var. rivale the obtuse leaves and especially the immersed stomata, 

 distinguish it ; the naked, smooth calyptra is also characteristic. 0. Sprucei is really 

 the only species which might be confused with it, but the more broadly rounded 

 summit of the leaves, usually showing the characteristic apiculus, and the much larger 

 cells are in that species quite distinctive. 



10. Orthotrichum Sprucei Mont. (Tab. XXXV. H.). 



Resembling O. rivulare but shorter and denser, softer, dull 

 green. Leaves more flaccid, somewhat variable in form, but 

 always broader in the upper part than in that species, usually 

 oval-oblong or widely elliptical, at apex broad, rounded, quite 

 obtuse or with a minute acute apiculus formed of about one row 

 of cells ; margin recurved to near apex; entire or nearly so at 

 summit ; nerve thinner and less prominent ; cells larger, the 

 basal laxer and more pellucid, the upper very large, about 20 p in 

 diameter, very distinct. Capsule immersed, a little longer, rather 

 less contracted below the mouth when dry, ribs a little less strong ; 

 processes more often only 8 ; other characters as in O. rivulare. 



Hab. On wood and trees by water ; frequent by mountain streams in the North 

 of England, elsewhere rare. Fr. summer. 



This very interesting species has only been found out of Britain in a few localities 

 in France and Belgium, and in one spot in N. America. In areolation and leaf form 

 it is quite distinct from the last, and the habit and fruiting characters present minor 

 but still not unimportant differences. The minute apiculus at the apex of the leaves 

 is very curious and distinct ; it is however frequently wanting, especially in the older 

 leaves. The stomata in this and the last species are so nearly covered by the over- 

 lapping cells as to be sometimes difficult to detect, and are, as is the case often with 

 the immersed forms, more easily found by the radiating cells of the surface layer than 

 by the form of the guard-cells. 



11. Orthotrichum Schimperi Hamm. (O. fallax Schp., 



Syn.) (Tab. XXXV. I.). 



Very small, in short, close tufts, not half an inch high, usually 

 much less, dark green. Leaves erecto-patent, imbricated and 

 straight when dry, small, oblong-lanceolate , rather broad, obtuse 

 or shortly acuminate ; margin recurved ; cells rounded-hexagonal, 

 distinct, not much incrassate, minutely papillose. Capsule very 

 small, immersed, oval-oblong with a short neck, when dry narrow 

 and slightly contracted below the mouth, ribs 8, rather strong, 



