MYXOMYCETES. 



275 



The Myxomycetes live upon decaying and rotting vegetable substances, such 

 as tan, rotten stems, and the like. While endowed with motion they either creep 

 over the surface of the substratum, or live in hollows and pores in its interior; 

 but for the purpose of reproduction they always come to the surface. When a 

 Myxomycete is entering the reproductive condition, the whole of its protoplasm 

 (the Plasmodium) becomes transformed into sporangia or large receptacles. In 

 most Myxomycetes the sporangia have the form of round, longish vesicles, sessile 

 or stalked, one or more millimetres in length; less commonly they form horizontal 

 tubes either cylindrical or flattened. The structure of the walls of these sporangia 

 is similar to that of ordinary cell-walls ; they sometimes exhibit similar thickenings 

 and stratification; they are colourless, or violet, brown, red, or yellow, according to 



Fig. 197, 



-A Plasmodium o( Didymium leticopus (after Cienkowski, X3S0) ; B a closed sporangium ot Arcyria incarnata 

 C after rupture of the wall / and extrusion of the capillitiuni cp (after De Bary, x 20). 



the species. In some, as Licea and Cribraria, the cavity of the sporangium is 

 entirely filled with small spores ; but generally the sporangium contains, besides the 

 spores, a structure called the Capillitium, consisting sometimes of small thin-walled 

 lubes anastomosing reticulately which are attached to the wall of the sporangmm 

 {e.g, Physarum); while in Arcyria (Fig. 197, O the wall of these tubes is furnished 

 with thickenings of an annular or wartlike or varying shape, projecting on the 

 outside. The capillitium of the genus Trichia consists of separate long fusiform 

 tubes not united to one another; their wall is thickened spirally like the spiral cells 

 of higher plants. In the Stemoniteae the pedicel which bears the sporangium 

 is continued into it and forms the so-called Columella, from which the branches 

 of the capillitium spring and anastomose reticulately. When the spores are being 

 disseminated, the rupture of the wall of the sporangium and the expulsion of the 



T 2 



