48 Mycetozoa of North America 



22. Physarum oblatum Macbr. Bull. Nat. Hist. S. U. Iowa 2: 384. 

 1893. 



Physarum ornatum{?) Peck, Kept. N. Y. State Mus. 31: 40. 1879. 

 Craterium Maydis Morg. Jour. Cin. Soc. Nat. Hist. 19: 15. 1896. 

 Physarum Maydis (Morg.) Torrend, Fl. Myx. 193. 1909. 



Plasmodium? Sporangia stalked, rarely sessile, globose or 

 subglobose, 0.4 to 0.6 mm. diam., yellow or pale yellow, rough- 

 ened; sporangial wall membranous, yellow, with innate closely 

 set clusters of yellow or pale yellow lime-granules. Stalk erect, 

 slender, furrowed, 0.3 to 0.8 mm. high, reddish brown, translu- 

 cent. Capillitium of many angular and branching yellow or pale 

 yellow lime-knots, connected by fairly long threads, sometimes a 

 Badhamia-VikQ network. Spores violet-brown, spinulose, 9-12 n 

 diam. 



Type locality: Iowa. 



Habitat: On dead wood, usually cotton wood poplar. 



Distribution: Common and abundant throughout the United 

 States, Canada, and the West Indies. 



Illustration: Lister, Mycetozoa cd. 3. pi. 32, figs, c-e, as 

 P. Maydis. 



This species forms small colonies with several or man>' on a 

 single log. The occasional sessile sporangia closely resemble 

 Badhamia decipiens, but are generally associated with colonies of 

 stalked sporangia on the same habitat. Still more rarely plasmo- 

 diocarps may be present with sessile sporangia. The species is 

 distinguished from P. auriscalpium by the long stalks, the uni- 

 formly smaller globose sporangia, and the evenly distributed 

 color. P. ornatum Peck is probably the same form, but the 

 opinion is uncertain, as my examination of the type specimen in 

 the New York State Museum discloses that only stalks remain. 

 Macbride's name must be accepted until an authentic and perfect 

 specimen from Peck is produced. Craterium Maydis, undoubt- 

 edly a Physarum, and regarded by Torrend and the Listers as a 

 distinct species, is merely a small form of P. oblatum. The state- 

 ment, frequently expressed, that its habitat is on corn stalks is a 

 myth. I have examined many corn stalks in the field without 

 results, and the only specimens here on that habitat are typical 

 P. oblatum. I have found the small form several times on other 

 habitats, and also forms of intermediate sizes, and there are no dif- 

 ferences between them and P. oblatum except size. 



