PHYSARUM 89 



decaying leaves or on rotten logs. The Plasmodium, at first colorless, as 

 it emerges for fructification becomes white, then yellow, spreading 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. 



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 called by Schweinitz P. polycephalum and, fortunately, 

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

 himself affirms the probable identity of Montagne's Didymium gyro- 

 cephalum with the Schweinitzian species, and uses Montagne's specific 

 name provisionally. For these reasons it seems proper to write the 

 species as above. 



This species is so common that its plasmodium and fructification may 

 be easily observed. Professor Morton E. Peck says of P. polycephalum: 

 "In one instance I observed a plasmodium for twelve successive days 

 on the surface of a decaying stump. During 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 yellow; and once, 

 shortly before fruiting, it became clear bright green. A heavy rain fell 

 upon the plasmodium but it appeared to sustain little injury and 

 ultimately developed normal sporangia." The plasmodium feeds 

 largely on the hymenium of various fleshy and subfleshy fungi, and 

 may readily be cultured on such substrata. See Howard (1931). 



The var. obrusseum (Berk. & Curt.) List, is merely a phase with the 

 sporangia more or less free instead of united. It seems to merge im- 

 perceptibly into the other forms. 



Widely distributed and common, from Maine and Canada to Wash- 

 ington and south to Nicaragua, Puerto Rico, British Guiana; France, 

 Rumania, Malay Peninsula, Japan. 



71. Physarum dictyospermum List. 



Jour. Bot. 43 : 112. 1905. 



Sporangia subglobose, short-stalked, erect, scattered, 0.5-0.6 mm. 

 in diameter, dull orange, dark chestnut or olive-brown, glossy, spo- 



