group, however, and since it consists wholly of microscopic fungi, need not be farther considered in this work.

In the Ascomycetes are included the sub-families Discomycetes, Pyrenomycetes, and Tuberacei. Of these the Discomycetes and the Tuberacei are the only groups which contain any of the mushrooms, and but few of these are large enough or sufficiently tender to possess value as esculents. A good example of the first (Discomycetes) is found in the Morel, and of the second (Tuberacei) in the Truffle.

In the Discomycetes or "disk fungi," the spores are produced in minute membraneous sacs, each sac usually containing eight spores. These spore sacs are imbedded in the flesh of the exterior and upper surface of the mushroom cap.

In the four classes, Hymenomycetes, Gasteromycetes, Discomycetes, and Tuberacei, therefore, are included all of the plants which are here designated under the generic term of "mushrooms."

Some idea of the relative numerical value of these classes may be obtained from the following figures given by the distinguished British mycologist, M. C. Cooke:

(The Tuberacei comprise a very small group of subterranean fungi, and comparatively few of the species are described.)

Saccardo in his Sylloge gives a total of 42,000 described species of fungi of all classes, including the most minute. Of these the Hymenomycetes include by far the largest number of edible mushrooms.

The family Hymenomycetes is divided into the following six orders: Agaricini, Polyporei, Hydnei, Thelephorei, Clavarei, Tremellini.

In the order Agaricini the hymenium is found on the under surface of the mushroom cap, covering pleats or gills, technically called lamellæ. These gills vary in character in the different genera, being "persistent in such as the Agaricus, Russula, and Lentinus, deliquescent (melting) in Coprinus, Bolbitius, etc. The edge of the gills is acute in Agaricus, Marasmius, etc., but obtuse and vein-like in Cantharellus, longitudinally channelled in Trogia, and splitting in Schyzophyllum."

In the Polyporei, pore-bearing mushrooms, the gills are replaced by tubes or pores. The tubes are little cylinders, long or short, pressed one against another, forming by their union a layer on the under surface of the cap, and the sporiferous membrane or hymenium lines their inner walls. Their upper end is always closed, while the lower extremity is open to permit the outward passage of the spores. The tubes are generally joined together and are not easily disunited. They are free, i. e., separable, in the sole genus Fistulina. As regards their attachment to the cap, the tubes may be firmly adherent as in the genus Polyporus or easily detached in a single mass as in Boletus, the fleshy form of the order Polyporei. They frequently leave a circular space of greater or less dimensions around the stem, or they adhere to or are prolonged upon it in such a manner that the orifices rise in tiers one above another. The color of the tubes, although not offering as characteristic varieties as that of the gills, changes nevertheless according to species and according to the age of the plant. The tubes may sometimes be of a different color