PHY S A RUM 53 



same Plasmodium. Where the substratum affords room the plas- 

 modiocarpous style prevails ; in narrower limits single sporangia stand. 

 The calcareous deposit on the peridium is usually very rich and under 

 a lens appears made up of countless snowy or creamy flakes. Forms 

 occur, however, in which these outer calcic deposits are almost en- 

 tirely wanting; the peridium becomes transparent, the capillitium 

 visible from without. Judging from material before us, this appears 

 to be the common presentation in western Europe. See also No. 5 

 following. 



Widely distributed. New England to the Carolinas, and Loui- 

 siana west to South Dakota and Nebraska, Iowa and Washington. 



5. Physarum bitectum List. 



Plate XIX., Fig. 16. 



1891. Physarum diderma Rost., List., Jour. Bot., XXIX., p. 260. 

 1894. Physarum diderma Rost., List., Mycetozoa, p. 57. 

 1911. Physarum bitectum List., Mycetozoa, 2nd ed., p. 78. 



Sporangia gregarious, subglobose, sessile or plasmodiocarpous, 

 smooth white or pallid, terete or somewhat compressed ; peridium dou- 

 ble, the outer wall calcareous, free and deciduous above, recurved and 

 persistent below; the inner, smooth, pale purplish, more persistent; 

 dehiscence more or less irregular beginning at the top ; capillitium of 

 large white nodules connected by short hyaline threads; spores gen- 

 erally spinulose, violaceous brown, 9-10 fi. 



As suggested by the author of this species it is properly a variety 

 of P. sinuosum; certainly is, as it presents itself in this part of the 

 world. Of the species last named we have compressed forms opening 

 by narrow fissure along their knife-edged summit, with scarce place 

 for capillitium at all between the approaching walls; again we have 

 colonies of sporangia quite terete, calcareous without, opening in 

 fragmental fashion at the top, displaying sometimes the thin membran- 

 ous inner wall but at length fissured and gaping as in the more usual 

 phase figured by authors, where the plasmodiocarp is simply com- 

 pressed but not extravagantly thin. Both types occur in the western 

 mountains, forms with and without calcium, fissured by wider or 

 narrower cleft, frotn the same Plasmodium; forms bilabiate and 



