134 Mycetozoa of North America 



1. Mucilago spongiosa (Leyss.) Morg. Bot. Gaz. 24: 56. 1897. 



Mucor spongiosus Leyss. Fl. Hal. ed. 2. 305. 1783. 



Reticularia alba Bull Uerh.Fr. pi. 326. 1786; Bull. Champ. 92. 1791. 



Spumaria alba (Bull.) DC. Fl. Fr. 2: 261. 1805. 



Plasmodium white or yellow (Lister). Aethalia composed of 

 elongate, compressed, lobed and branched, gray sporangia, arising 

 in loose or compact clusters from branching strands of the mem- 

 branous hypothallus, clothed with a thick, fragile, deciduous 

 covering of crystals of lime, 2 to 6 cm. long, 1 to 6 cm. wide, and 

 1 cm. or more thick; sporangial wall membranous, colorless or 

 purplish. Columella membranous, hollow, compressed, some- 

 times absent. Capillitium a network of widely branching, anas- 

 tomosing, stout, purplish brown or colorless threads, often with 

 dark calyciform thickenings, hyaline at the extremities; sporangia 

 sometimes penetrated by tubular processes which open externally, 

 and either perforate the lobes of the sporangia, or continue into 

 the threads of the capillitium. Spores dull purple, strongly 

 spinulose, 10-13 m diam. (Plate 10, fig. 3.) 



Var. solida (Sturg.) Lister, Mycetozoa ed. 2. 138. 1911. 

 Spumaria alba (Bull.) DC. var. solida Sturg. Colo. Coll. Pub. Sc. Ser. 12: 29. 

 1907. (N. Y. B. G. nos. 12770, type; 12785, cotype.) 



Aethalia pulvinate, compact, 2 to 5 cm. diam., 1 to 3 cm. 

 thick; lime-crystals small, often nodular; capillitium scanty, 

 colorless, irregular; spores spinulose, 9-11 n diam. 



Type locality: Germany. 



Habitat: On leaves, twigs, and dead wood. 



Distribution: Throughout the United States and Canada. 



Illustration: Lister, Mycetozoa ed. 3. pi. 117. 



This species is closely related to Didymium cruslaceum, and in 

 some intermediate specimens the connection is clearly shown by 

 more or less distinct sporangia even to the partly developed outer 

 deciduous walls of D. cruslaceum. Var. solida is not rare wher- 

 ever the species is fruiting in abundance, usually on cottonwood 

 poplar and associated with Fuligo intermedia, or on manure piles 

 and composts accompanied by F. cinerea. It appears to be the 

 highest aethalioid formation of the species, but there are all 

 sorts of intermediates between it and the forms approaching 

 D. cruslaceum. Var. solida forms compact, firm aethalia, some- 

 times appearing externally like Fuligo septica var. Candida, but 



