PHYSARUM 47 



P. plumbeum Fr. belongs here. It has similar spores; the only 

 difference is a less calcareous peridium and more scattered habit of 

 fructification with more nearly regular, depressed-globose sporangia. 

 P. cinereum Pers. as cited by Link (Mag. Ges. Nat. Fr. Berl. 3 : 27, 

 1809) is apparently a badhamia, but may be P. vernum, while P. gri- 

 seum is probably the present species. Specimens collected by Wingate 

 and distributed by Ellis and Everhart as N. A. F. 2085, should be 

 referred to Didymium melanospermum. 



Var. scintillans Brandza, Bull. Soc. Myc. Fr. 44 : 260, 1929, is de- 

 scribed as having isolated metallic blue or bronze sporangia with few or 

 no calcareous nodes. The bluish form is described as having spores 

 9-10 n, the bronze, 12-14 fx. Its position must be regarded as uncertain. 



Careful examination of a wide range of American collections sug- 

 gests that the large-spored forms are not P. vernum and constitute a 

 distinct variety of P. cinereum, perhaps a closely allied species. 



Common and cosmopolitan. 



4. Physarum gilkeyanum Gilbert 



Am. Jour. Bot. 19 : 133. 1932. 



Sporangia gregarious, globose or clavate, sessile, but narrowed at 

 the base, 0.4 to 0.8 mm. in diameter, 0.7 to 0.9 mm. tall; peridium 

 hyaline, gray when without lime but usually covered with a thin even 

 layer of grayish white lime, brittle, breaking irregularly, the inner 

 surface rough, the lime covering forming a reticulation of thin wrinkles 

 over the entire sporangium; capillitium of fine hyaline threads, a 

 dense, rigid, fine-meshed net that retains the form of the sporangium 

 after the peridium breaks away, the lime-knots white, few, in the 

 upper part of the sporangium small and more or less rounded, in the 

 base of the sporangium tending to be long branching and somewhat 

 badhamioid with larger meshes in the capillitium; spores dark violet 

 in mass, globose, warted, violet-brown under the lens, 9-11 ix. 



Oregon. In leaf mold under deciduous trees and brush. 



5. Physarum megalosporum Macbride 



N. A. Slime-Moulds ed. 2. 63. 1922. 

 1917. Physarum melanospermum Sturgis, Mycologia 9 : 323, non Pers. 



Sporangia gregarious, sessile or short-stipitate, depressed, annulate, 

 or at least umbilicate above, white, rarely roseate, 0.5-0.8 mm. in 

 diameter; stipe, when present, short, thick, black or dark brown, 

 hypothallus none; columella none, but capillitium sometimes massed 

 toward the center; capillitium strongly calcareous, the delicate net 

 bearing an abundance of irregular white nodules; spores dark pur- 



