202 Mycetozoa of North America 



plasmodic granules 1.5-2 fi diam. The cups are very shallow, 

 often almost obsolete. The larger sporangia approach C. elegans, 

 but the violet tints are those of C. violacea. 



Genus 28. DICTYDIUM Schrader, Nov. Gen. PI. 11. 1797. 



Sporangia stalked, globose; sporangial wall formed of numer- 

 ous ribs extending from the base nearly to the apex, connected by 

 slender, transverse threads, the intervening wall evanescent, or 

 persistent as a shallow cup. 



Type species: Dictydium umhilicatum Schrad. 



1. Dictydium cancellatum (Batsch) Macbr. N. A. Slime-Moulds 

 172. 1899. 



Mucor cancellatus Batsch, Elench. Fung. Coniin. 2: 135. 1789. 

 Dictydium umbilicatum Schrad. Nov. Gen. Pi. 11. 1797. 

 Dictydium longipes Morg. Jour. Cin. Soc. Nat. Hist. 15: 143, 1893. (N. Y. 

 B. G. no. 5265, type material.) 



Plasmodium purple-black (Lister). Total height 1 to 2 mm. 

 Sporangia gregarious, stalked, nodding, subglobose or depressed, 

 often umbilicate above and sometimes below, brown or brownish 

 purple, 0.5 to 0.7 mm. diam. Sporangial wall forming a net with 

 nearly square meshes, composed of numerous rigid, longitudinal 

 ribs, connected by slender, transverse threads, often breaking up 

 into an irregular net at the top; calyculus usually rudimentary or 

 lacking, sometimes well developed. Stalk subulate, bent or 

 twisted at the slender top, dark brown or purplish brown, two to 

 eight times the height of the sporangium. Spores pale reddish or 

 purplish, 5-7 m diam., nearly smooth, usually with one or more 

 large, dark, plasmodic granules on the spore wall. (Plate 12, 

 FIG. 5.) 



Var. fuscum Lister, Jour. Bot. 36: 120. 1898. 



Sporangia nodding, smaller and browner than the type, bell- 

 shaped or contracted at the base, with a well-defined cup or 

 calyculus. 



Type locality: Germany. 



Habitat: On dead wood. 



Distribution : Common and abundant throughout the United 

 States and Canada; Puerto Rico; var. fuscum not so common but 

 widely spread. 



