Physarum 71 



51. Physarum contextum Pers. Syn. Meth. Fung. 168. 1801. 



Diderma flavidmn Peck, Rept. N. Y. State Mus, 28: 54. 1876. (N. Y. B. G. 



no. 11798, type material.) 

 Physarum Mortoni Macbr. N. A. Slime-Moulds ed. 2. 58. 1922. 



Plasmodium yellow (Lister). Sporangia sessile, subglobose or 

 obovoid, 0.4 to 0.6 mm. diam., or reniform and elongate on a 

 broad base, free or more often crowded in colonies, often angled 

 by mutual pressure, rounded above or flattened, smooth and yel- 

 low, ochraceous, or white; sporangial wall double, the outer layer 

 thick with dense deposits of lime, often breaking away in the 

 upper part from the thin, colorless, inner layer. Capillitium with 

 scanty hyaline threads and numerous large, irregularly branching, 

 white or yellowish lime-knots, occasionally densely massed in the 

 middle. Spores dark violet-brown, spinulose, 10-13 /x diam. 



Type locality: Europe. 



Habitat: On dead leaves, twigs, mosses, and wood. 



Distribution: Common throughout North America. 



Illustration: Lister, Mycetozoa ed. 3. pi. 55. 



This species is variable in the manner of sporangial formation. 

 Usually, the sporangia are densely compacted in small clusters, 

 but may be perfectly free and sometimes with vestiges of short 

 stalks. The walls may be uniformly dense with lime, and the 

 tops confluent, appearing as a pseudo-aethalium, or, the lower 

 parts only may be stout, persisting as distinct cups. These varia- 

 tions appear in different clusters of the same large development. 

 P. Mortoni is one of these phases, and unworthy even of varietal 

 rank. Similar conditions are present in many other species. 

 The color of the spores of P. contextum ranges from dark to light 

 purplish brown, and the spines, often prominent, may be much 

 fainter, and scattered, or arranged irregularly with smooth areas 

 between. 



52. Physarum conglomeratum Rost. Mon. 108. 1874. 



Plasmodium? The description of Physarum contextum applies 

 to this species in general except that the spores are pale violet- 

 brown, almost smooth, 8-10 /x diam. 



Type locality: Europe. 



Habitat: On habitats similar to those of P. contextum. 



Distribution: *Antigua, *Louisiana, *Pennsylvania, Quebec, 

 *Tennessee. 



