BASID'IOMYCE'TES (basidium, see below + Gk. /415KnTES, mushrooms, fungi). Probably the largest of the great groups of Fungi in number of species. It includes the smuts (Ustilaginales), the numerous rusts (iiredinales), and the immense assemblage of forms called mushrooms, toadstools, bracket fungi, and puffballs, besides many smaller groups. The higher forms of Basidiomycetes are readily distinguished by the peculiar method of spore-formation. The end of a filament (hypha) becomes swollen, and then puts out generally four small processes, which become spores at tached to the end of the parent filament by deli cate stalks (`sterigmata'). Such a filament is called a 'hasidium' (dimin. of Gk. /3iiais, basis. base, foundation), and its spores `basidiospores.' The basidium is in all essentials the same, whether the fructification he a mushroom, toad stool. bracket-fungus, puffball, or some simpler structure. The smuts and rusts, however, pre sent conditions that have only within compara tively recent years been related to the basidium. This matter is discussed in the article on Fumi, and for an account of the structure and habits of these groups, see USTILAGINALES and UREDINALES.
In this brief account, attention must be given chiefly to the mushrooms, toadstools, bracket fungi, and puffballs, which comprise the bulk of the Basidiomycetes. In these groups the spore bearing surface (hymenium) covers specialized regions of the body, the most familiar being the knife-blade-like plates or gills of most toad stools (Agrieales), the minute pores in the under side of the bracket-fungi (Polyporales), and the pointed teeth in the hynales. In the puffballs, the spore-bearing surface lines a labyrinth of chambers ('gleba') in the interior, which become quickly disorganized so that the mature puffball is hardly more than a capsule ('peridium') inclosing a powdery mass of spores. The structures called toadstool, bracket-fungus, or puffball, are really only the fructifications of extensive thready bodies (mycelium) that pene trate the substratum in all directions. Thus the toadstools and mushrooms (edible toadstools) that come up on the lawns and iu pastures have been formed and nourished by a cobweb-like growth of filaments that spread.; through many
square feet of the soil. Such forms often ap pear in more or less complete circles ('fairy rings') ; which indicates that the body is advanc ing through the soil from some centre of infec tion.
The toadstool develops from a small ovoid body beneath the surface of the ground. In this structure the parts of the mature fructification are differentiated, so that the latter may quickly expand at maturity. The stalk ('stipe') then rapidly elongates, carrying aloft the cap ('pileus') and frequently leaving at the base a sort of cup ('volva') into which the stalk fits. In some forms there is also a ring just below the cap (pileus), which ring is the remnant of a membrane that held the pileus folded against the stalk. The presence or absence of a volva or ring, the structure of the gills, and the color of the spores are the most important systematic The puffballs (Casteromycetes) present vari ous conditions with respect to the structure of the parchment-like envelope (peridium), which may be simple, rupturing irregularly; or com posed of several layers and provided with special openings for the escape of spores. The 'Earth stars' (Geaster) and the 'Bird's-ilest fungi' (Nidulariales) are highly developed types.
Very different is the group of the 'Stink-horns' (Phallales). This order comprises a series of forms very remarkable in their structure and development, but whose habits take away any natural beauty. The masses of spores are ex posed on a stalked structure that emits the most penetrating odor Of carrion. It is interesting to know that this scent attracts flies, and probably serves a useful purpose to the plant in dis tributing the spores.
For an extensive account of the Basidiomy cetes, consult Engler and Prantl, Die vat iirlichen. Pflanzenfamilien (Berlin, 1S99); and in English, Stevenson, British H ymenom yeetes (London, 1886). A large number of books on toadstools and mushrooms have been published in America, the most extensive being Atkinson, Studies of American Fungi (Ithaca, 1900). See :Mush ROOM ; FUNGI; and plates illustrating these articles.
characters of toadstools. Thus, the members of Amanita, the most dangerous genus among the toadstools, has white spores, a volva, and a ring.