54 



THE MYCETOZOA 



continuation, the columella, is, as de Bary showed, an axial structure 

 secreted in the interior of the young sporangium (Fig. 14, a-e). In 

 the formation of these sporangia the basal portion of the stalk is 

 formed first and additions are made to the apex as the protoplasm 

 climbs up this axial support. In Stemonitis fusca and splendens the 

 stalked sporangia may attain a height of 20 mm. 



In addition to the skeletal or supporting structures of the spore- 

 bearing stage above mentioned, another is present in many genera 

 the hypothallus. This consists of a network of strands or a con- 

 tinuous film, formed of the same material as the other supporting 

 structures, extended over the substratum, and forming the base 

 on which the sporangia are inserted (cf. Fig. 13, d). Its presence 

 apparently depends on the occurrence of the secretion, in the later 



Fia. 13. 



a, sporangia of Physarum nutans, Pers., x 15. b, piece of sporangium wall, with groups of 

 lime granules, capillitium threads, with lime-knots (k) and spores of Physarum nuta*s, x 210. 

 c, spore of same, x 450. d, sporangia of Craterium pedunculatum, Trent, each with a discoidal 

 hypothallus at the base of the stalk, x 17. e, sporangia of Chondrioderma testaceum, Host., 

 showing the double sporangium Avail (outer layer with lime, inner membranous), and in the 

 upper sporangium the columella, x 15. /, threads of the capillitium of the same, x 280. g, 

 group of crystals of lime from the wall of Spumaria alba, x 210. h, a crystalline disc from 

 the sporangium wall of Lepidoderma tigrinuam, Bost., x 210. (After A. Lister, 18.) 



stages of the plasmodial condition, of the substance which dries into 

 the supporting material its reticular or continuous character corre- 

 sponding with the state of diffusion of the plasmodium during ita 

 formation. 



The sporangium wall may consist of two layers as in Chondrioderma 

 (Fig. 13, e), where the outer is densely charged with lime granules, 

 and the inner is membranous and free from lime. In some species 

 of Craterium (Fig. 13, d) the upper portion of the sporangium wall 

 forms a lid, which readily falls away, exposing the contents. In 

 Dictydium (Fig. 1 4,/) and Cribraria the wall of the mature sporangium 

 is represented wholly or in part by an open network, through the 



