It is to the _volva_ or _cup_, then, that we must turn for the one fixed permanent character by which this genus is to be identified.
[Illustration: Agaricini or Gill-bearing Fungi]
Our introductory description of the Amanita presents the most perfect botanical type of a large division of the fungus tribe, the _Agaricaceæ_, or gill-bearing mushrooms, one of the two great orders of fungi which include the large majority of edible species.
A brief consideration of the general classification of fungi will not be out of place at the head of this chapter.
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. _Hymenomycetes._ Hymenium, or spore-bearing surface, _exposed_ and conspicuous, as seen in the common mushroom and all Agarics and Polyporei.
2. _Gasteromycetes_ (_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 [kônis], meaning dust, the entire fungus having a _dust-like_ appearance. Mildew forms a good example of this family.
4. _Hyphomycetes_, from the Greek [hypha], 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.
In this order the hymenium, or spore-bearing surface, is inferior, _i.e._, on the under side of the pileus, and is spread over lamellæ or gills, which radiate from the stem of the fungus, and each of which may be separated into two filmy flat divisions.