Each black mold plant is a branching tubu lar filament, which has few cross partitions. One part of the plant usually grows in the sub stance of the organic matter, and another grows upward into the air. (Fig. 8). The former ab sorbs food matter, while the latter bears re productive organs, as in the water molds. The ends of the aerial branches enlarge as in the two preceding families, but instead of forming zoospores, the protoplasm in the terminal seg ments forms many small spores, each covered with a cell wall. These spores are the homo higues of the zoospores in previous families, but as the plants are not aquatic, these zoo spores have ceased to be aquatic olso. With a good cell wall to protect- their protoplasm, they may be blown about in the air without drying qp. It is in this way, in fact, that black molds are propagated, the air currents carrying the spores sometimes for long distances, and when they fall upon organic matter under favorable conditions they quickly rise to a new crop of mold plants. On the filaments which penetrate the nutrient substance„or grow over its surface, are to be found (rarely, how evet, in the common species) sexual organs somewhat resembling those of the two,preced ing families. (Fig. 9).
Insect Fungi (Entomophthbracece) are somewhat similar to black molds, hut are parasitic in the body tissues of insects, an ac cordingly show considerable structural modi fications. (Fig. 10).
Phylum Carpomycetese. , The Higher This immense phylum, containing over 60,000 recognized species and probably twice as many, if not more, not yet studied, seems to have arisen from chlorophyll-bearing plants of the phylum Rhodophycese, the Red Sea weeds. These are mostly marine, although many fresh-water species are known. They re produce sexually by the union of a non-motile sperm with the elongation of the oogone, termed trichogyne. The male nucleus passes down this to the egg nucleus with which it unites. The fusion nucleus thus produced di vides very freely and the daughter nuclei pass out into many branching threads whose ter minal cells (carpospores) are the reproductive cells of the plant. The whole structure of oogone, branching threads and carpospores is a ((spore-fruit" and may or may not be sur rounded by a protective structure of vegetative cells. In the Higher Fungi we find similarly a spore-fruit arising as a, result of the sexual process. The ultimate cells are of three kinds, depending upon which one of the three classes is under consideration. (See VEGErasta KING DOM and PLANTS, MORPHOLOGICAL EVOLUTION OF). These classes are the Ascomyeetew, Basidiomy cetea. and Teliosporem. Beside these there is
a large group of fungi, certainly belonging to this phylum hut which in the lack of knowledge as to their sexual reproduction cannot with certainty be assigned to any one of these classes. These are the Imperfect Fungi. All the plants of this phylum possess branching threads with numerous cross walls (septa) and usually one or two nuclei to a cell. Asexually they pro duce by conidia, cells cut off from the ends of unmodified or specially modified threads. The cells so produced possess walls and are dis tributed by the wind, rain, insects, etc.
Sac Fungi (class The distinguishing mark of the plants of this class faces of their hosts, from which they obtain food by means of root-like absorbing organs, which penetrate the host cells. Certain branches form spores by the simple process of separating their terminal cells in succession and this is done so abundantly that the spores form pow dery masses on the surface of the hosts. These spores float away on wind currents, and those that germinate on similar hosts give rise to new plants.
The sexual organs (egg-cells and antherids) occur on the creeping filaments, and are short lateral branches, the former somewhat thicker than the slender antherids. (Fig. 12). The two tome in contact with each other, and the protoplasmic contents of the antherid pass into the egg-cell fertilizing it. As a result the egg cell sends out one or more branches, the end cells of which develop into asci, while from below the egg-cell there grows up a cellular, globular covering, constituting the outer wall of the fruit, and enclosing the asci. The spores in the asci, when set free by the rupture of fruit and ascus walls, germinate and on similar hosts give rise to new plants. These fruits are usually blackish and may be seen by the naked eye as minute globular bodies on the mass of filaments. (Fig. 13).
Truffles (Tuberacea') are eagerly sought for as table delicacies, their large subterranean fruits being highly favored by epicures. Their life history is not well known. They are sap rophytic, living on the organic matter in the soil in forests. Little is known as to their early life, and the formation of their non-sexual spores, but these are thought to be somewhat like' those of the powdery mildews.
is that the spores which occur in their fruits de velop in certain end cells and remain enclosed within the cell wall until matured. (Fig. 11). These spore-containing cells have been aptly likened to sacs (Latin asci; singular, ascus) and from this we derive the name of the class.