68 Mycetozoa of North America 



46. Physarum echinosporum Lister, Jour. Bot. 37: 147. 1899. 



Plasmodium? Sporangia scattered, forming chalk-white, 

 usually curved plasmodiocarps, strongly compressed laterally, 

 dehiscing along the thin upper ridge; sporangial wall of two 

 layers, the outer smooth, eggshell-like, charged with minute 

 lime-granules, separating from the inner membranous, iridescent, 

 pale purplish layer. Capillitium consisting of numerous smooth 

 white lime-knots, irregular in shape and size, connected by short 

 hyaline threads. Spores purple, marked with strong ridges and 

 spines, 8 /x diam. 



Type locality: Antigua. 



Habitat: On dead leaves. 



Distribution: *Known only from the type locality. 



Illustration: Lister, Mycetozoa ed. 3. pi. 53. 



47. Physarum bivalve Pers. Ann. Bot. Usteri 15: 5. 1795. 



Reticularia sinuosa Bull. Herb. Fr. pi. 446, fig. 3. 1789; Bull. Champ. 94. 



1791. 

 Physarum sinuosum (Bull.) Weinm.; Fries, Syst. Myc. 3: 145. 1829. Not 



P. sinuosum Link. 1809. 



Plasmodium white (Lister). Sporangia scattered, sessile with 

 a contracted base, or forming elongate, sinuous, or branching 

 plasmodiocarps, laterally compressed with parallel sides, the up- 

 per ridge flattened and finally splitting longitudinally, white, 

 gray, or yellowish; sporangial wall double, the outer layer with 

 more or less dense deposits of lime, smooth or reticulate, the inner 

 layer wrinkled and colorless, membranous, usually adhering to 

 the outer layer. Capillitium consisting of numerous white, often 

 branching, large or small lime-knots connected by rather short 

 hyaline threads. Spores violet-brown, spinulose, 8-10 /x diam. 



Type locality: Europe. 



Habitat: On dead leaves and ground matter. 



Distribution: Common everywhere in North America. 



Illustration: Lister, Mycetozoa ed. 3. pi. 49, as P. sinuosum. 



This species usually forms sporangia and plasmodiocarps in 

 the same development. It reflects in a marked degree the 

 abundance or scarcity of lime in the habitat. In limestone 

 regions, the outer wall may be white, densely encrusted with lime; 

 and with little lime in the soil, it may be dark and almost limeless. 



