132 Mycetozoa of North America 



concealed under the crust of lime surrounding the sporangia. 

 Columella small, irregular, depressed, hardly evident in the sessile 

 forms, white or pale buff, with rather scanty deposits of lime in 

 the form of nodules. Capillitium consisting of colorless or pale 

 violet branching threads, 0.5-1 n diam., often with minute fusi- 

 form thickenings. Spores purplish gray, strongly spinulose, 

 10-13 M diam. (Plate 10, fig. 2.) 



Type locality: Europe. 



Habitat: On dead leaves and twigs. 



Distribution: Colorado, Iowa, North Carolina, Ohio, On- 

 tario, Pennsylvania, *South Dakota, Tennessee, Virginia, *Wash- 

 ington. 



Illustration: Lister, Mycetozoa ed. 3. pi. 111. 



A remarkably interesting species. The sporangia, covered 

 with crystals of lime and on membranous stalks which are expan- 

 sions of the hypothallus, are surrounded at a considerable distance 

 by an outer smooth but fragile crust of compacted lime-crystals, 

 like an inverted jar for each sporangium. The outer wall or 

 crust seems to form separately and disappears rapidly, so that 

 most of the collections show only fragments. When the outer 

 crusts are gone completely, the clustered mass of inner sporangia 

 looks like phases of Mucilago spongiosa, where the outer crust or 

 cortex has disappeared. The species provides a good example 

 for study of the relationship between the sporangial and aethalioid 

 forms of fructification, and the transition from one to the other. 



19. Didymium fulvum Sturg. Mycologia 9: 327. 1917. (N. Y. 

 B. G. no. 11338, type.) 



Plasmodium? Sporangia in clusters, usually sessile, sub- 

 globose, concave beneath, 0.5 to 0.8 mm. diam., or forming 

 curved plasmodiocarps, pale tawny from an abundant covering 

 of yellowish lime-crystals; sporangial wall membranous, spotted 

 with orange-yellow, clothed with large sharp-pointed crystals of 

 lime. Stalk when present, short, orange, enclosing lime-crystals, 

 and merging into strands of tawny hypothallus which are rough 

 with crystalline deposits. Columella conical, or almost obsolete, 

 orange, enclosing lime-crystals. Capillitium an abundant net- 

 work of purplish threads, hyaline at the extremities. Spores 

 purplish brown, closely warted, or marked with curved, branch- 

 ing lines, paler and smoother on one side, 12 14 ii diam. (Plate 

 2, FIGS. 4-6.) 



