These plants greatly resemble Mosses in their appearance, but they differ in their construction. The theca has no lid, but bursts into valves; and it generally contains not only sporules, but tubes formed of curiously twisted threads, called elaters. Jungermannia and Marchantia have a calyptra, which the other genera are without; and in Jungermannia the theca has a sort of sheath, which is sometimes called the calyx. There are also stalked granules called anthers, and warts which form on the leaves, and break up into a kind of sporules.
[Illustration: FIG. 150--USNEA FLORIDA. (_Old Trees._)]
[Illustration: FIG. 151.--RAMALINA FASTIGIATA. (_Rocks and Trees._)]
[Illustration: FIG. 152.--CORNICULARIA HETEROMALLA.--(_Old Trees._)]
Though these plants are said to have no leaves, they consist almost entirely of a kind of leafy stem, called a frond or thallus, the branches of which are called podetia (see _a_ in _figs._ 150, 151, and 152). The spores or sporules are produced in what are called shields (_b_ in _figs._ 149, 150, and 151), which are generally embedded in the thallus, and which, when they are cup-shaped (as in _fig._ 150), are called scyphæ, and when flat (as in _fig._ 151), apothecia. The sporules, which are very numerous, are inclosed in receptacles of various forms, which are embedded in the shields. Some of the commonest lichens are _Usnea florida_ (_fig._ 150), and _Ramalina fastigiata_ (_fig._ 151), both of which are found on old oaks, and are generally called grey moss; and _Cornicularia heteromalla_ (_fig._ 152) is a brown mossy-looking lichen, often found on the bark. Other more interesting lichens are--the Iceland-moss (_Cetraria islandica_), the Reindeer-moss (_Cenomyce_, or _Cladonia rangiferina_), the Cup-moss (_Cenomyce pyxidata_), and the Orchil (_Rocella tinctoria_).
The Fungi are divided into several distinct sections; the most important of which may be called the Mushroom tribe. The largest genus in this division is Agaricus, and the plants belonging to it consist of a stipe, or stalk (_c_ in _fig._ 149), surmounted by the pileus or cap (_d_). When the mushroom first appears, the stalk is covered by a thin membrane, called the veil (_e_), which unites the cap to the lower part; but as the mushroom grows, this veil is rent asunder, and it either entirely disappears, or only a small part of it remains round the stalk, which is called the annulus or ring. Under the cap are the gills or lamellæ, which are of a dark reddish brown; and attached to these are the thecæ, containing the sporules or seed. In the common Mushroom (_Agaricus campestre_), and all the eatable kinds, the gills are pink when the veil breaks, which it does very soon, and they become afterwards nearly black; but in all the poisonous kinds, the veil is longer before it breaks, and when it does so, the gills are pale, and frequently nearly white, without becoming darker; the smell is also quite different. The Mushroom tribe, which includes all the Fungi that carry their sporules in the part above the stem, is divided into two sections, viz., those with caps, like the Mushroom, and those which are slender and entire, but club-shaped in the upper part, like _Clavaria helvola_, a fungus often found in meadows, which resembles the stamen of an orange-lily.