Simple Plants Without Chlorophyll — Fungi 179 



wood, etc. The vegetative body consists of masses of septate hyphae 

 which penetrate the substratum. Fleshy, fruiting bodies called sporo- 

 phores are produced for reproduction purposes (Fig. 41). Each sporo- 

 phore typically consists of a broad, caplike or umbrella-shaped pileus 

 (pil' eus) (L. pileus, cap) and a stalklike stipe (L. stipes, stalk). On 

 the undersurface of the pileus are gills which are thin plates of compact 

 hyphal tissues and which bear club-shaped basidia (ba-sid'ia) (Gr. 

 basis, base). The latter bear numerous hasidiospores (Fig. 65), each 

 attached by a slender sterigma (ster-ig'ma) (Gr. sterigma, support). 

 In the case of the common, edible, field mushroom (Psalliota [Agaricus] 

 campestris), a single sporophore may produce nearly two billion hasidio- 

 spores, each of which may germinate to form a new hypha. At certam 

 times there may be fusion between two cells of adjacent hyphae (by a 

 process equivalent to a sexual process), producing a binucleated cell 

 which is the hasidium. This nucleus will divide to form four nuclei, one 

 for each of the four hasidiospores. Each of the latter is pinched off from 

 the sterigma and scattered by the wind. There are several hundred 

 species of mushrooms and toadstools but only a comparatively few of 

 them are poisonous. Most of the latter belong to the genus Amanita. 

 Unless the collector of wild mushrooms is familiar with the specimens he 

 collects, he should take no chances with the deadly species. It is better 

 to forego the use of mushrooms rather than be sorry later. 



2. Bracket Fungi (Pore Fungi). — The bracket fungi or shelf fungi are 

 members of the family known as pore fungi because the underside of the 

 caps (shelves) contain hundreds of tiny tubes which appear as pores on 

 the lower surface. The internal tissues around these tubes produce club- 

 shaped basidia which bear basidiospores (Fig. 42). The latter escape 

 through the pores. 



The hyphae of tree-inhabiting shelf fungi secrete enzymes which digest 

 the tissues of the wood and bark and absorb organic compounds from 

 these tissues. The shelflike sporophores described above are often tough 

 and woody. In certain species they may be perennial, forming new 

 spore-producing hyphae in annual layers, year after year. Shelf fungi 

 are common causes of wood decomposition, and parasitic species often 

 kill living trees. Among the important wood-rotting pore fungi is Meru- 

 lius lacrymans which causes the common "dry rot" of wood. 



3. Smuts. — Smuts are produced by a group of smut fungi parasitic on 

 flowering plants, in which the irregular masses of septate hyphae pene- 

 trate the tissues of the host plant. They are called smuts because the 



