90 MOSS HABITATS. 
walls the richer the spoils as a rule. So prolific, however, in mosses are 
these habitats, that I shall not be able to mention a tithe of what may be 
found by an industrious worker, and hence shall confine my remarks to a 
few of the more frequent species, such as Tortula muralis, T. marginata, 
Grimmia apocarpa, G. pulvinata, Bryum capillare, B. cespiticium, B. 
argenteum, Didymodon rubellus, and Pottia lanceolata. 
Tortula muralis is one of our most frequent mosses, often fillmg up 
the interstices between the bricks of an old wall from its base to its top, 
growing in hoary, bluish-green tufts; the leaves are oblong with blunt 
tips, terminated by white hair-like points, very hoary in some of the 
varieties ; the leaf-margin is recurved, leaf-cells minute and opaque in 
upper part, transparent and elongated below; the capsule is erect; lid 
shortly beaked ; fringe of thirty-two teeth, beautifully twisted. 
Tortula marginata is a more local species, partial to damp stone 
walls, and usually growing on the surface of the stone. At first sight 
not unlike the foregoing, but has narrower leaves, with the margin 
thickened, not recurved, and terminated by a minute green point. The 
fruit-stalk, too, is yellow in this species; reddish in muralis. Fruit 
characters similar to the last. 
Grimmia apocarpa is a not unfrequent denizen of wall tops, forming 
deep green loose tufts. The upper leaves are hair-pointed, with 
recurved margins. The capsules are sessile among the surrounding 
(pericheetial) leaves. Lid slightly beaked; fringe of sixteen teeth, dark 
red, marked with transverse bars and sometimes perforated. 
Grimmia pulvinata is a very common species, growing on walls, and 
often in great masses on thatched roofs, forming round, hoary, cushion- 
like masses. The leaves are densely crowded, and suddenly terminate 
by long white hair points. Fruit-stalk longish and bent downwards, so 
that the capsule is often hidden among the leaves. The lid has a 
straight beak; the teeth of the fringe sixteen, deep red and sometimes 
cloven at the tips. Calyptra mitriform, five lobed at the base. 
Bryum capillare is very fond of old walls, and is very frequent; 
often occurs in large dense dark green masses. The leaves are 
spreading when moist, but strongly twisted when dry, somewhat oblong 
and abruptly hair-pointed. Capsule somewhat pear-shaped, and 
pendulous; lid conical, with a minute point ; fringe double ; outer fringe 
reddish-brown, beautifully barred; inner fringe membraneous, paler ; 
spores small, green. The peristome of this common moss is a most 
beautiful object for the microscopist. 
Bryum cespiticium is also very frequent, growing in close compact 
tufts, of a yellowish or green colour. Usually very much like the last 
at first sight; but in this the leaves are erect (not twisted) when dry, the 
lid yellow, not red as in capillare, and the spores minute and yellow. 
Bryum argenteum may be readily known by its beautiful silvery 
foliage. The leaves are closely imbricate, (overlapping ;) capsule 
pendulous, and passing abruptly into the fruit-stalk. Green forms, 
however, occur ; but may at once be known by the closely-imbricated 
leaves, with large cells. 
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