The fungi as thus described are found in four of the grand divisions (phyla) of the vegetable kingdom.
Phylum, Myxophycem. The Slime Alga. — Here are gathered a thousand or so species of microscopic aquatic plants in which the cells have a very low organization. No distinct nucleus is present, and the coloring matter in the typical plants pervades the whole cell, and is of a bluish or brownish-green color instead of a bright green as in higher plants. They re produce by simple fission, and by the produc tion of spores. There is no hint of any sexual reproductive process. They occur in ponds, pools and streams, to which they give a green ish color by their great numbers. In decaying they usually give off a fetid odor.
While the typical Slime Alga are greenish and are known as green slimes —many have become parasitic or saprophytic, and have lost their green color. These colorless species are known as Bacteria, and are the lowest of the fungi'.
Bacteria (Fig. 1) are then to be regarded as colorless green slimes, their lack of color being due to their parasitic or saprophytic habits. Some species are minute rounded cells of remarkable minuteness. To these the generic name Micrococcus has been given, and many speciei have been recognized by botanists. Other genera with spherical cells are Strepto , coccus, Staphylococcus, Sarcina, etc. Other bacteria consist of cylindrical cells which tend to adhere end to end in filaments or rods. In the genera Bacillus and Bacterium the rods are straight or little curved, and short or of mod erate length, while in Vibrio and Spirillum the rods are more or less spirally curved. In still other genera, as Crenothrix, Leptotkrix, etc., the rods are elongated. The study of Bacteria in relation to diseases of man and other ani mals and of plants, and to soils, etc., has de veloped into the science of Bacteriology (q.v.). Many botanists now, on that account, do not include Bacteria among the Fungi. See BAC TERIA.
Phylum Chlorophycea and Phylum Si These plants, of which there are probably nearly 2,500 species, may very properly be called sea-weeds, since they are typically aquatic, living in the salt and fresh waters of the earth. Typically they are bright
green, and the cells of which they are com posed have well-formed nuclei. However, the chlorophyll is confined to definite portions of the protoplasm, and is not diffused throughout the cell. Some of the lower species are spher ical, rounded cells, but for the most part they consist of filaments of cylindrical cells; or in some instances they are masses of cells con stituting leafy-stemmed plants. They repro duce by fission as in the Slime Alga, but in addition all, or nearly all, Slime Alga repro duce sexually also. In the simplest cases of sexuality, two equal and similar cells detached from older plants fuse into a new and larger cell, and then this new cell grows into a new plant. Sometimes the new cell becomes covered with a thick wall, and for a time ceases activity as a °resting spore,* before it develops into a new plant.
While most of the plants of these two phyla are green plants, several hundred species have become parasitic or saprophytic in habit (Figs. 2 to 10) and have therefore lost their color, and become fungi. Among these are the following families, namely: Gall Fungi (Synchytriacee) are beyond reasonable doubt to be regarded as hystero phytic forms of the one-celled class (class Protococcoidece) of the first of these two phyla. These fungi consist of single cells which enter the cells of their living host plants and there enlarge, feeding on the host cells and causing an irritation of the tissues which often causes swellings which may be minute or in some cases very large (e.g., wart disease of potato tubers caused by Synckytrium endobioticum). The fungus cell eventually breaks up internally into numerous minute zoospores which escape in various ways and infect new host cells. 2). The family Chytridiacee (Fig. 3) which are mostly parasitic in aquatic algae and fungi arc probably closely related to these or to the next forms.