A fungus is a cellular cryptogamous (flowerless) plant, nourished through its spawn or mycelium in place of roots, living in air, and propagated by spores.

Fungi - mycetes - are naturally subdivided into two great divisions:

1. Sporifera - those in which the spores or reproductive bodies are naked or soon exposed, as shown in illustration on page 79.

2. Sporidiifera - in which the spores are enveloped in sacs or asci. These resemble in shape the cystidium of illustration on page 79.

The first of these divisions - the Sporifera, or naked-spored fungi - is again subdivided into four families, as follows:

1. Hymcnomycetes. Hymenium, or spore-bearing surface, exposed and conspicuous, as seen in the common mushroom and all Agarics and Polyporei.

2. Gasteromycetcs (gaster, a belly). Hymenium, or spore-bearing surface, enclosed in a more or less spherical case, called the peridium, which ruptures and expels the spores at maturity in the form of dust, as in the puff-balls.

3. Coniomycetes, from the Greek kwvis, meaning dust, the entire fungus having a dust-like appearance. Mildew forms a good example of this family.

4. Hyphomycetes, from the Greek vфa, meaning a thread. Thread-like fungi, the filaments being more conspicuous than the spore masses, of which group blue-mould affords an illustration.

The Hymenomycetes (1) is again subdivided into six orders, the discrimination being based on the diverse character of the spore surface. The first of these orders is the Agaricini, or gill-bearing fungi, to which our present chapter will be confined.