80 THE MYXOMYCETES 



of P. notabile except that the lime-knots are said to be dark yellow- 

 brown. 



56. Physarum pusillum {Berk. b° Curt.) Lister 



Mycetozoa ed. 2. 64. 1911. 

 PI. VI, Figs. 105, 106. 



1873. Didymium pusillum Berk. & Curt., Grev. 2 : 53. 



1881. Physarum nodulosum Cke. & Balf., Rav. N. A. F. Exsic. 479. Not 



published. 

 1889. Badhamia nodulosa (Cke. & Balf.) Massee, Jour. Myc. 5 : 186. 

 1891. Physarum calidris Lister, Jour. Bot. 29 : 258. 

 1896. Craterium nodulosum (Cke. & Balf.) Morg., Jour. Cin. Soc. Nat. Hist. 



19 : 15. 

 1899. Physarum nodulosum Cke. & Balf. ex Macbride, N. A. Slime-Moulds 51. 



Sporangia gregarious, small, stipitate, globose, 0.4-0.6 mm. in di- 

 ameter, grayish white at first, becoming white as the spores are freed, 

 with a brown base, the sporangium walls thin, rugose, more or less 

 encrusted with lime, breaking up irregularly; stipe slender, longer 

 than the sporangium, attenuate upward or even, bright brown, rugose, 

 merging into the shallow, cup-like base of the sporangium; columella 

 none; capillitium with lime-knots more or less abundant, white, often 

 uniting, somewhat badhamioid; spore-mass black; spores by trans- 

 mitted light pale lilac-brown, minutely warted, 10-12 fx. 



One of the smaller species of the genus, by its proportionally long 

 stipe and small round sporangium reminding one somewhat of P. glo- 

 buliferum; much smaller, however, and in every way different. The 

 generic characters are mixed, and the species has been accordingly 

 variously referred. The lower part of the peridium is sometimes per- 

 sistent after the dehiscence, and in that respect suggests Craterium. 

 But this character is not constant, and even at best the persisting 

 part is very small, not greater than in P. melleum, for example. On 

 the other hand, the capillitium in some sporangia is strongly calcareous, 

 suggesting Badhamia, but in most sporangia the physarum characters 

 are sufficiently clear. 



The name Physarum nodulosum seems not to have been effectively 

 published until 1899, although the specific name nodulosa was used 

 by Massee (1889) and Morgan (1896). Didymium pusillum Berk. & 

 Curt, was published in 1873. The type at Kew contains two species, 

 this and a didymium. But Sturgis reported that the specimen in 

 Curtis' herbarium, presumably a co-type, shows only the physarum. 

 On the face of the record, Physarum pusillum (B. & C.) Lister is the 

 valid name. 



Canada to Pennsylvania and Iowa; cosmopolitan. 



