64 THE MYXOMYCETES 



1829. Diderma globuliferum (Bull.) Fr., Syst. Myc. 3 : 100. 



1876. Physarum petersii Berk. & Curt. var. farlowii Rost., Mori. App. 6. 



1876. Didymium subroseum Pk., Rept. N. Y. State Mus. 28 : 54. 



1878. Physarum albicans Pk., Rept. N. Y. State Mus. 30 : 50. 



1893. Physarum columbinum Macbr., Bull. Lab. Nat. Hist. Iowa 2 : 384, non 



Pers. 

 1896. Cytidium globuliferum (Bull.) Morg., Jour. Cin. Soc. Nat. Hist. 



19 : 10. 

 1896. Physarum relatum Morg., Jour. Cin. Soc. Nat. Hist. 19 : 26. 



Sporangia gregarious, stipitate, globose or slightly depressed above, 

 about 0.5 mm. in diameter, pale blue-gray to pure white or sometimes 

 rosaceous; stipe calcareous, extremely brittle, at least equal to the 

 sporangium, usually longer, slender, slightly wrinkled, white, pallid 

 or yellow, when long tapering upward; columella white, conical, some- 

 times obsolete; hypothallus scanty, inconspicuous; capillitium dense, 

 but delicate, persistent, a close network of hyaline threads, with white 

 or yellowish nodes sparingly thickened and calcareous, many without 

 lime; spore-mass brown; spores violet by transmitted light, minutely 

 warted, the warts in indistinct clusters, 7.5-9 ju. Plasmodium yellow 

 or greenish yellow according to published records. We have a collec- 

 tion (S. U. I. 1485), typical in every respect, which developed from a 

 pale violet Plasmodium, without a trace of yellow. 



This species, very common eastward, is at once very beautiful and 

 very variable. Its several phases have been again and again observed 

 and described too often by distinct specific or varietal names. A 

 form from New York, with long, white stems and almost pure white 

 sporangia, is P. albicans Peck. Forms occur like P. albicans, but flushed 

 with rose throughout. From New England, specimens sent Rosta- 

 finski were by him deemed a variety of P. petersii Berk. & Curt., and 

 called P. petersii var. farlowii Rost. By this name the species has been 

 generally distributed in this country. Most gatherings of this species 

 have small, somewhat ochraceous sporangia, and pale yellow, or some- 

 what rusty stipes. These latter, with somewhat heavier stem, represent 

 Physarum simile Rost. A form collected sparingly in Iowa has short, 

 white stipes and blue-gray sporangia one-third larger than observed 

 in the eastern types. This was recorded as P. columbinum Macbr., a 

 name already in use. The spores in the Iowa specimens are also a little 

 larger, 8-10 (x. Pale cyanic and roseate forms also sometimes occur 

 in late fruitings. 



In all phases the persistent tenacity of the capillitium is a striking 

 characteristic well noticed by Fries (Syst. Myc. 3 : 101): "Peridia a 

 gleba omnino libera, dein tota diffracta, evanescentia, . . . capillitio 

 compacto forma servata persistente." The peridium, except a small 



