PHYSARUM 55 



18. Physarum bivalve Pers. 



Ust. Ann. Bot. 15: 5. 1795. 

 PI. IV, Figs. 57, 58, 59. 



1791. Reticular ia sinuosa Bull., Champ. 94. 



1828. Angioridium sinuosum (Bull.) Grev., Scot. Crypt. Fl. 310. 



1829. Diderma valvatum Fr., Syst. Myc. 3 : 109. 



1829. Physarum sinuosum (Bull.) Weinm. ex Fr., Syst. Myc. 3: 145, non Link. 

 1849. Carcerina valvata Fr., Summ. Veg. Scand. 451. 

 1869. Diderma contortum Fuck., Symb. Myc. 341. 



Fructification plasmodiocarpous, the plasmodiocarp creeping in 

 long vein-like reticulations or curves, laterally compressed, or some- 

 times sporangiate, distinct and crowded, sessile; peridium double, the 

 outer layer thick, calcareous, fragile, snow-white to gray or yellowish, 

 the inner delicate, colorless, the dehiscence by more or less regular 

 longitudinal fissure; capillitium strongly developed with abundant 

 white, calcareous granules; spores minutely spinulose, dull violet, 

 8-10 ix. Plasmodium reported as pale gray, or nearly white, but typical 

 specimens are sometimes associated with a yellow Plasmodium. 



Easily recognized at sight by its peculiar form, bilabiate and sinuous. 

 Except for its microscopic structure, perfectly described by Fries, 

 Syst. Myc. 3 : 145. Habitat various, but not infrequently the upper 

 surface of the leaves of living plants, a few inches from the ground. 

 Plasmodiocarpous and sporangiate fructifications often occur side by 

 side, or merge into one another from the same plasmodium. Where the 

 substratum affords room the plasmodiocarpous 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 deposits are almost entirely wanting; the peridium becomes 

 transparent, the capillitium visible from without. Judging from mate- 

 rial before us, this appears to be the common presentation in western 

 Europe. The degree of compression is very variable. Some collections 

 show compressed plasmodiocarps opening by narrow fissure along their 

 knife-edged summit, with scarce place for capillitium at all between the 

 approaching walls; others take the form of colonies of sporangia almost 

 terete, calcareous without, opening in f ragmen tal fashion at the top, 

 displaying sometimes the thin membranous inner wall, but at length 

 fissured and gaping as in the more usual phase figured by various 

 authors, where the plasmodiocarp is simply compressed but not ex- 

 travagantly thin. Both types occur in the western mountains, forms 

 with and without calcium, fissured by wider or narrower cleft, from 

 the same plasmodium; forms bilabiate and forms opening at first to 



