Chapter 4 

 THE MYXOMYCETES 



. The Myxomycetes, or slime molds, are fungus-like organisms 

 which, in their vegetative or assimilatory phase, consist of a 

 naked, multinucleate mass of protoplasm called a plasmodium, 

 and in their reproductive phase consist of encased spores. Their 

 relationship to fungi and to animals has long been a much-dis- 

 cussed subject, as is indicated by the name Mycetozoa, which is 

 frequently applied to them. Such early workers as Micheli and 

 Fries placed them among the puffballs, and it is easily understand- 

 able that such well-known species as Lycogala epideiidnim and 

 Fiiligo septica should have been regarded as puffballs. 



The development of a slime mold is typified by that of F. 

 septica. It is cosmopolitan, and its fruit bodies may be found on 

 logs, around stumps, or on lawns and flowerbeds. They are yel- 

 lowish, tawny, cushion-like structures about 3 to 6 cm in largest 

 diameter and 2 to 3 cm thick. The cortex is friable, foamy, and 

 calcareous. The interior is filled with violaceous, spherical spores 

 with knotted threads (capillitia) interspersed. The spores are 

 usually disseminated bv winds. In moist weather the spore walls 

 open to emit swarm cells (myxamoebae), which ingest bacteria 

 and fungus spores, assimilate them, and grow to become a large, 

 multinucleate, naked mass of protoplasm (plasmodium). The 

 Plasmodium moves in amoeboid fashion to the surface of the sub- 

 stratum and in its entirety becomes a fruit body (aethalium). 

 Each nucleus is invested with a wall during the transformation 

 of a Plasmodium into an aethalium, and the inert materials (left- 

 overs) become the cortex and capillitium. 



Present-day knowledge of the slime molds began with a series 

 of studies by de Bary covering a period of 10 years, which were 

 assembled in his monograph in 1864. He early observed that 

 the spores of Hemitrichia vesparhim give rise not to germ tubes, 

 as do those of fungi proper, but to amoeboid flagellates. For 



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