198 A Monograph of the Mihwgastres. 



cing irregularly or in a stellate manner ; inner wall, when 

 present, very thin, containing no lime, often iridescent; colu- 

 mella present or absent; threads of capillitium thin, without 

 lime ; either sparingly bifurcating, or branching and anasto- 

 mosing to form a more or less dense net. 



Clwndriodcrma, Rost., Mon., p. 167 ; Cooke, Brit. Myx., p. 36 ; 

 Schroeter, p. 123 ; Sacc, Syll., v., 7, pt. I, p. 362. 



The characteristics of the present genus are, a well-developed 

 capillitium not containing lime, and the outer wall highly 

 charged with lime, externally perfectly smooth and porcelain- 

 like. Closely allied to Didymiuin; in fact so closely allied, that 

 leaving out imaginary or book distinctions, the only point of 

 difference consists in the outer surface of the wall in Bidymium 

 never being porcelain-like, but always more or less granular 

 or pulverulent. Such a division is convenient from the system- 

 atic point of view, as to whether it is of generic value or not 

 is a question that cannot perhaps be decided in the present 

 state of knowledge as to what constitutes affinity in the 

 Myxogastres. The space between the outer and inner wall I 

 do not find sufficiently constant to adopt as part of the generic 

 character, its presence depends on the contraction of the spore 

 forming mass of protojilasm, due to expulsion of water after 

 the outer calcareous wall has become rigid ; in C. suhlcderitium, 

 the contraction of the inner spore-mass takes place before the 

 outer calcareous wall becomes rigid, hence the latter also 

 collapses and becomes normally umbilicate above. The same 

 condition of things may sometimes be met with in species that 

 usually have a space between the two walls. 



Bistrib. Temperate and tropical regions; most abundant in 

 the former. Species 34. 



Stch-Gcn. Leangium. Sjwrangmvi siMtting in a stellate manner. 



A. Columella ^iresent. 



Chondrioderma floriforme, Rost. (figs. 58, 59). 



Gregarious, springing from a well-developed hypothallus ; 



sporangia broadly obovate, stipitate, yellowish-brown, dehiscing 



