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Myxomycetes

plasmodia, spores, slime, body and called

MYXOMYCETES, mik'so-mi-sU!'tez (Neo-Lat.

nom. pl., from Gk. it my,ra, mucus +14knr,mykr's, fungus). A group of organisms commonly called slime molds. Certain phases of their life history are very animal-like, but the final fruetifieation has many plant characteristics, and as the forms are described and classified by the fructification the work has naturally fallen within the province of botany. They are here treated as one of the great groups of the fungi (q.v.). The purpose of the fructification is the production of multitudes of very minute spores. The spores germinate in moist situations on the soil and in humus, giv ing rise each to a motile protoplasmic body pro vided with a cilium (Figs. 0.7,8). These swarm cells swim around in the moisture, increasing in number by division (fission). After an active period they become more quiet and creep around like arneebx ( Figs. 1,2, 3), finally approaching one another and fusing in pairs, or perhaps sev eral together. Such fused groups become centres of attraction to many hundreds of swarmers, which contribute their substances to the common mass. The result is a large protoplasmic body, called a plasmodium (Fig. 9), which moves over the surface of the humus and into crevices like a gigantic amoeba. Its food is largely bacteria and other fungi, which are taken directly into the pro toplasmic body and digested, the hard and worth less portions being discarded.

Vegetating plasmodia shun the light and seek moisture. But these habits arc reversed when the fructification is to be formed ; the plasmodia then come to the light and take position in the driest situations that they can find. This is the

time when plasmodia are most conspicuous and are frequently found on stumps, bark, and hu mus. The largest plasmodia may cover several square inches, but most of them are much small er, and some are no larger than a pin-head.

The form of the fructifications is exceedingly various, some being large and irregular, and others with an extraordinary &heavy and com plexity of structure, hut the general history of spore formation is much the same. The plasmo dium excretes a great deal of material (and fre quently mineral matter) which forms the wall of the spore-case (sporangium) and its stalk if present (Fig. 10). A filamentous network called the capillitium may also be developed inside the spore-ease, its function being to distribute the spores. The protoplasm which remains after these activities divides up into minute rounded bodies which, investing themselves with walls, become the spores. The plasmodia of slime molds have been favorite subjects of observation by physi ologists, who find here the largest masses of pro toplasm that can be studied.

For a general account consult: Engler and Prantl, Dic noturlichen nzenfamilien zig, 1887) ; and for special descriptive treatment. Lister. A Monograph of the llyrefozort (London, 1894) ; McBride, Tie North American Slime Moulds (New York, 1899).