Another species, _Sphæria discifor´mis_, is also common on birch-sticks. It differs from the last in the tubercles being perfectly flat; the spores are also longer, straight, and spindle-shaped (fusiform). PERISPORÁCEI.--_Erys´iphe guttáta_ (Pl. VIII. fig. 33) is a member of this family. It appears on the under side of the leaves of the common hazel as a pale spot; and on closely examining it with the naked eye, little black dots are seen scattered on the surface. These are the capsules (conceptacles), which are seated upon straight white filaments. The filaments (_fulcra_) are six or seven in number, and are placed under the capsule, like the legs of a stool (fig. 34); they are rigid, and swollen or inflated at the base (fig. 35). The asci are broad and short, and contain only two spores. _Erysiphe maculáris_ is the very destructive hop-mildew; and other species are common on various plants. _Chætómium elátum_ (Pl. VIII. fig. 29) resembles little tufts of brown hairs, occurring upon decaying herbaceous stems. The capsule (fig. 28) is crustaceous, and covered with interlaced, rough, branched hairs (fig. 28 _b_). The spores (fig. 28 _a_) are oval, with a little point at one end (apiculate). PHYSOMYCÉTES (φῦσα, bladder, μὑκης, fungus).--The Fungi belonging to this order include some of the commonest moulds growing upon decaying vegetable substances; while others are found upon leaves, &c. The flocci are generally very evident; and the spores are contained in little naked, bladder-like capsules (_peridíola_) at the ends of free filaments. MUCORINI.--In this family we have the common mould of paste, _Múcor mucédo_ (Pl. VIII. fig. 36). It is easily recognized by the little spherical capsules terminating the long and tufted fruit-stalks (pedicels), which are perceptible to the naked eye. Each capsule consists of a simple enlarged cell, the cavity of which is separated from that of the stalk by a septum. They are white at first, subsequently becoming brown and black. The minute crowded spores (fig. 36 _s_) are at first oblong, afterwards spherical. In the centre of the capsule is a club-shaped body, or _columel´la_ (fig. 36 _a_), formed by the elevation and inflation of the septum. A beautiful little Fungus of this family, apparently referable to the genus _Acrostalag´mus_ (Pl. VIII. fig. 37), is sometimes found upon soft decaying stems. The main filaments are soft, smooth, and not septate. The pedicels are very brittle, whorled, dichotomously branched, scabrous, and terminated each by a little scabrous spherical vesicle (fig. 37 _a_), containing two or three oblong spores. ANTENNARIÉI.--In this family is _Racódium_ (or _Antennária_) _celláre_, the Wine-cellar Fungus, forming the well-known cobweb-like masses hanging from the walls, &c. The little black capsules are seated upon slender septate filaments, and contain numerous round spores.