There are more species of sac fungi than of all other kinds. Their fruits range in size from very minute to many inches in extent. They include some of the most harmfully parasitic plants as well as many which live saprophy tically upon refuse organic matter. Among the many families (more than 100) in this class, the following may be noticed: Powdery Mildews (Erysiphacer) are the cause of many serious diseases of wild and cultivated plants; e.g., rose, apple, cherry, goose berry, ash, etc. The plant body consists of branching filaments which creep over the sur Their fruits are formed under ground. The sexual organs, which possibly precede the de velopment of the fruits, have not yet been dis covered. The fruits of the common truffles of Europe are from one to two inches in diameter, and warty and dark colored externally. (Fig. 14). Internally they consist of a soft, whitish tissue, in which are numerous cavities, each containing several asci. Practically nothing is known as to their propagation. A few little known species occur in America, but in Europe they are common. See TRUFFLE.
Black Fungi (SPheriacee and numerous related families) are typically parasites which grow in the tissues of higher plants, and whose small black fruits are formed on the surface of the host. Here again we are evidently dealing with plants related to the powdery mil dews, but with an increased parasitism. They are known to form non-sexual spores much as in the powdery mildews. Their fruits also re semble the fruits of the powdery mildews, and probably result from a fertilization, but thus far the sexual organs have evaded discovery.
Closely related to the foregoing and differing principally in possessing a bright color and fleshy or leathery structure are the members of the Family Nectriacew. Asexual and sexual the fruits (Fig. 17) are globular when young, but as they mature they open out into shaped structures (Fig. 17), in the concave sur reproduction are similar to the same phenom ena in the SpItzeriales. Several species of Nec trio (Fig. 15) cause serious cankers on apple twigs, etc. Ergot of grains (Spermcedia or Claviceps) also belongs in a closely related family.
Cup Fungi (Pecizacece and related families) are typically saprophytes (Figs. 16 and 17), growing in the tissues of decaying plants, as rotten logs, sticks, etc. In these fungi the plant is filamentous and grows through the decaying tissues as slender white, branching threads. Non-sexual spores resembling those of the pow dery mildews are known for some species. Sex ual organs consisting of a globular egg-cell and a slender anthenid are found on the creep ing filaments. (Fig. 19). Fertilization • takes
face of which are found many asci (Fig. 18). It will readily be seen that were these cup fruits to remain closed, their structure would be closely similar to that of the fruits of the powdery mildews or black fungi. However, the fruits of the cup fungi are often of con siderable size, sometimes being as large as five or six inches in diameter.
Lichens (see article LICHENS) are now re garded as nearly related to the cup fungi and black fungi. (Fig. 20). In the essentials they agree with those fungi, but they are usually treated separately because their parasitism on various small alga leads to the production of place as in powdery mildews, with a similar result, the fruits, however, being at length shaped instead of globular. In many species peculiar vegetative structures, the study of which for a long time led botanists to neglect their evident relationship to fungi which were not parasitic on alga. There are several fam ilies of the lichen-forming fungi, aggregating between 2,500 and 3,000 species.
Yeasts (Saccharomycetaceer) are here briefly referred to in order to call attention to the excessive degradation which they have suf fered. Although they consist of single cells, or short chains, they are now regarded as greatly reduced sac fungi. They grow on sugars, starches and other carbohydrates, and one re sult of their activity is the formation of alcohol, while at the same time carbon dioxide is set free. It is for the alcohol that yeasts are used in breweries and distilleries, and it is for the escaping carbon dioxide gas that they are used in the making of bread. See YEAST.
Phylum Teliosporese.— The fungi of this phylum consist entirely of parasites upon higher plants. They are often exceedingly destructive. The characteristic distinction from the preceding phylum is the formation of a thick-walled telio spore. This is formed as the ultimate product of a sexual union. From this teliospore there arises sooner or later a short thread (Bromy celium) upon which are produced four (some times more) small "sporidia" which give rise to the new fungus when they fall upon the right host. In this phylum we find parasitism brought to its highest development. The fungus has so adapted itself to the host that it continues to live within the host tissues for a long time without causing much inconvenience, only prov ing destructive when it enters upon its fruiting stage. The two chief groups (orders) are the rusts and smuts.