70 
A. E. GIBBS-NOTES ON MOSSES. 
elevated to catch the passing breeze so as to be wafted to a suitable 
habitat. In the water-mosses of course the non-utility of a seta is 
evident. The capsule resembles a kind of urn, and usually dehisces 
by a lid (operculum), which falls off when ripe. Sometimes, how¬ 
ever, the lid is absent, and the capsule dehisces by valves, as in the 
case of the Andreaceae—mosses which always grow on dry quartzose 
rocks. The capsule and lid are usually covered by a calyptra or 
veil, which falls off either before or with the operculum. In the 
j Polytricha the veil is hairy, and resembles the cap which Robin¬ 
son Crusoe is generally represented as wearing; and hence it has 
acquired the popular name of “ Crusoe’s Cap.” After the lid and 
calyptra have been removed, a series of beautifully-arranged teeth, 
called the peristome, is generally revealed. These teeth are hygro¬ 
in etric, and play an important part in the economy of moss life. In 
wet weather they close over the top of the open capsule, and both 
prevent the escape of the spores during a period unsuitable for their 
conveyance from place to place, and also protect them from moisture. 
When the air becomes drier, they again open out, and allow of the 
diffusion of the spores. So delicate are these teeth, and so readily 
affected by humidity, that their movements are easily detected under 
a low power of the microscope, or with the naked eye. When 
breathed upon, they close, and as the influence of the moisture of 
the breath passes away they open out again, often with a spring, 
jerking the spores out of the capsule. In number, these teeth are 
either four, or some multiple of four. In some cases, as, for 
instance, in the order Hypnacese, the peristome is found to be double, 
there being two rows of teeth instead of one. In some instances 
these teeth are absent, and, when the lid is removed, the mouth of 
the spore-case is entirely unprotected, while in other cases it is 
closed by a narrow membrane. In the Tortulce the teeth are 
beautifully arranged in the form of a long spiral column. This may 
be distinctly seen in the most common species, T. muralis , which 
may be met with on any wall, for it is the most abundant of our 
mural mosses. 
Besides the usual mode of multiplication by spores, mosses are 
also propagated by buds, which rise from the roots, and by granules, 
which are produced either on the midrib, as in Pottia cavifolia, on 
distinct peduncles, as in Aulacomnium, or in rosettes, as in Tetrapis 
pellucida. In some cases new plants are even produced at the tips 
of the leaves. Many of the mosses, too, have a wonderful power 
of increase by self-extension. As they are, in the main, aerial 
vegetables, deriving their nutriment partly from the soil, but in a 
large degree from the air, it is not infrequently that we find the 
base of a tuft quite dead and decaying, and wrapped in what Ruskin 
calls “the funeral blackness” of the moss, while the upper part is 
healthy and green and growing. This is especially the case with 
the Sphagnaceee , where the plant gets its living principally from the 
moisture of the bog, the past year’s growth decaying and forming 
nutrient matter for the young shoots of the same plant. 
Mosses are easily divisible into two great classes—the Acrocarpi, 
