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. The Morel tribe includes those Fungi which have their sporules in the stipe, and it is in two divisions; the first of which includes those which, like the Morel (_Morchella esculenta_), have a pileus, or cap, like a mitre; and the second, those which have the pileus curving upwards, like a cup, as in Peziza. A third tribe includes those which, like Tremella, are of a jelly-like substance; and in a similar manner all the numerous genera are arranged. Among these the most remarkable are the Truffle (_Tuber cibarium_), which is found buried in the earth, and the curious Fungi called Blight and Mildew, which belong to several different genera, and which appear on the leaves and fruit of other plants. ORDER CCXX.—ALGÆ.