96 THE NORTH AMERICAN SLIME-MOULDS 



Sporangia spherical or irregular, impressed, gyrose-confluent, hel- 

 velloid, umbilicate below ; peridium thin, ashy, covered with evanes- 

 cent yellow squamules, fragile; stipe from an expanded membrana- 

 ceous base, long-subulate, yellow; spores smooth, violet, 9-11 fx. 



A most singular species and well defined is this, occurring in 

 masses of decaying leaves or on rotten logs. The Plasmodium at first 

 colorless; as it emerges for fructification, white, then yellow, spread- 

 ing far over all adjacent objects, not sparing the leaves and flowers of 

 living plants; at evening slime, spreading, streaming, changing; by 

 morning fruit, a thousand stalked sporangia with their strangely 

 convoluted sculpture. The evening winds again bear off the sooty 

 spores, and naught remains but twisted yellow stems crowned with a 

 pencil of tufted silken hairs. August. 



Although Rostafinski's description of this species is accurate and 

 marks exactly a Tilmadoche and is very different from his description 

 of Physarum polymorphum, nevertheless it is probable that both de- 

 scriptions have reference to the same thing. All specimens on which 

 both species were based were American; P. polymorphum, North 

 American. But the only North American form to which reference 

 can be made is that by Schweinitz called P. polycephalum and, for- 

 tunately, sufficiently described. Furthermore, Rostafinski, under T. 

 gyrocephala, himself affirms the probable identity of Montagne's 

 Didymium gyrocephalum with the Schweinitzian species, and uses 

 Montagne's specific name provisionally. For these reasons it seems 

 proper to write the species as above. 



Widely distributed and common, from Maine and Canada to 

 Nebraska, and Washington and south to Nicaragua. 



This species is so common that its Plasmodium and fructification 

 may be easily observed. Professor Morton E. Peck, who has been 

 for years a close observer of the vegetative phases of our Iowa species, 

 says of P. polycephalum: "In one instance I observed a Plasmodium 

 for twelve successive days on the surface of a decaying stump. Dur- 

 ing this period it crept all around the stump and from top to bottom 

 several times. At one time the color was bright yellow; at another, 

 greenish yellowt; and once, shortly before fruiting, it became clear 

 bright green. A heavy rain fell upon the Plasmodium but it ap- 



