The Sarcodina 231 



(69). The diet may influence color of the plasmodium, since some species 

 become pink in association with Serratia marcescens (69). The pigment 

 of Physarum polycephalum is a pH-indicator, changing from yellow- 

 green at pH 8.2 to a deep red-orange at pH 1.0 (136). Certain species 

 with yellow pigment apparently require light for completion of the life- 

 cycle, while several non-pigmented species develop sporangia equally well 

 in light and in darkness (44). 



The Plasmodium is holozoic, feeding largely on bacteria and other 

 microorganisms. A number of species have been grown in cultures with 

 a variety of microorganisms as food (19, 44, 60, 100). In addition, Fiiligo 

 septica, BadJiamia foliicola, and several others have been grown in pure 

 cultures on autoclaved yeast (25), but the specific food requirements of 

 these organisms are yet to be determined. 



The Eumycetozoina occur on rotting leaves and logs, and the plasmo- 

 dium usually grows in or beneath such decaying materials. The plasmo- 

 dium penetrates decaying wood by extending slender processes through 

 the interstices and, under experimental conditions, may pass through 

 filters with pores measuring about 1.0[a (92). Shortly before sporulation, 

 the Plasmodium creeps to an exposed position, sometimes on trunks or 

 stems of nearby plants, where conditions will facilitate desiccation and 

 dispersal of spores. Subsequent behavior varies in different species. In 

 the simpler cases a plasmodium merely gives rise to a compact flattened 

 mass, or aetJiaUinn (Fig. 5. 23, A), or to an irregularly lobate body 

 (plasmodiocarp) which retains to some extent the outline of the plasmo- 

 dium (Fig. 5. 23, B). In either case, the entire mass becomes enclosed in 

 a membrane and may be considered a single large spore-case (sporocarp). 

 More often, the plasmodium produces individual sporangia (Fig. 5. 23, 

 C-I), stalked in many species but not in others. 



The sporangia usually begin development as dense areas which become 

 segmented into knob-like masses. In many cases, the young sporangium 

 undergoes vertical growth, followed by differentiation of a stalk and a 

 spore case; in others, the sporangia remain sessile. The surface of the 

 sporangium typically becomes enclosed in a resistant wall (peridium), 

 which is commonly wrinkled at maturity. In stalked types, the peridium 

 is usually continuous with the covering of the stalk, and the stalk extends 

 to the substratum to end in a basal network, the hypothallus. Inside the 

 peridium, a capillitium (a network of threads or bands) is often devel- 

 oped, although lacking in Cribraria, Licea, and related genera. The first 

 indication of the capillitium in Physarum polycephalum (60) is the ap- 

 pearance of lacunae within the sporangium. These channels develop into 

 hollow threads whose junctions (nodes) become filled with calcium salts 

 as the sporangium approaches maturity. In other species, calcium may be 

 deposited throughout the capillitium, may be limited to the peridium or 

 its inner surface, or may not be deposited at all. The capillitial net, per- 



