The fructification of the Fungi occurs in two distinct forms, in one of which the seeds or spores are naked, and situated at the ends of slender cells or filaments, whilst in the other the spores are contained in usually flask-like cells, called asci, similar to those occurring in the Lichens. In a few Fungi, antheridial organs, called spermogonia, as in the case of the Lichens, have also been detected. The Fungi are divided into six Orders, from each of which a few species may be selected to illustrate their structure more in detail. HYMENOMYCE´TES (ὑμἠν, membrane, μὑκης, fungus). This is the highest Order of Fungi, containing a large number of genera and species; as examples of which may be mentioned the common Mushroom, Toadstools, &c. Their general structure may be illustrated by the examination of the common Mushroom (_Agar´icus campes´tris_); the species figured (Pl. VII. fig. 1), however, being _Agaricus micáceus_, which is common at the root of trees, the bottom of decaying posts, &c. The vegetative part of the fungus consists of a cotton-like mycelium, which is composed of slender, colourless, interwoven filaments, popularly known as the spawn. The portion commonly called the mushroom corresponds to the fructification, and consists of certain parts visible to the naked eye. These are an expanded portion at the top, forming a hemispherical cap, receptacle, or _píleus_ (_pileus_, a cap), and a stalk, or _stípes_, upon which the cap is supported. On the under surface of the cap are a number of nearly parallel, radiating, dark-coloured plates or _gills_, somewhat resembling the gill-plates of a fish. The dark colour of the gills arises from the presence of the spores, which are coloured, although in some species they are white. The surface of the gills, upon which the spores are situated, is called the _hyménium_ (ὑμἠν, membrane). The spores (Pl. VII. fig. 2 _a_) are microscopic and very minute, and are situated at the ends of little stalks or points (Pl. VII. fig. 2 _b_), called _sterig´mata_ (στἡρυγμα, a prop), which are four in number, and consist of prolongations of the colourless cells of the hymenium; and these cells are the _basid´ia_ (βασἱδιον, a little base). The detection of the basidia requires great care, as they are very minute and transparent; the best way to observe them is to cut a very small portion from the uninjured edge of one of the gills with a fine pair of scissors, and to examine it in water. If the gills have been bruised, the spores are easily rubbed off, and their connexion with the basidia destroyed.