118 Mycetozoa of North America 



1. Didymium difforme (Pers.) Duby, Bot. Gall. 2: 858. 1830. 

 Diderma difforme Pers. Tent. Disp. Meth. 9. 1797. 



Plasmodium colorless or yellow (Lister). Sporangia scat- 

 tered, pulvinate, on a broad base, or forming plasmodiocarps 

 0.4 to 2 mm. or more long, smooth, white; sporangial wall of two 

 layers, the outer a thin eggshell-like crust of densely combined 

 minute crystals of lime, separating from the iridescent membran- 

 ous inner layer, which is purplish or colorless above, yellowish 

 brown and thickened at the margin. Floor of sporangium an 

 orange or purplish membrane with scanty deposits of small lime- 

 crystals. Capillitium rather scanty, consisting of coarse or 

 slender, purple or colorless, flattened threads, usually broad at 

 the base, branching dichotomously, and slender above. Spores 

 dark purple-brown or purplish gray, faintly and closely warted, 

 with a pale area of dehiscence, 11-14 ^u diam. 



Van. comatum Lister, Jour. Bot. 39: 8. 1901. 



Capillitium profuse, of slender, straight, branching threads, 

 not thicker below, dark or colorless; spores purplish gray. 



Type locality: Europe. 



Habitat: On dead leaves, herbaceous stalks, and twigs. 



Distribution: California, Colorado, Kansas, Massachusetts, 

 New York, Ontario, *Oregon, Pennsylvania, *Washington; var. 

 comatum, *Pennsylvania, Quebec. 



Illustration: Lister, Mycetozoa ed. 3. pi. 104. 



D. difforme and the two following species, D. qiiitense and 

 D. trachysporum, constitute a group the members of which are 

 very much alike in their general appearance when observed with 

 a hand-lens, and are separated mainly by their spore-characters. 

 Their habitats also are similar, often on composts, or under 

 shrubbery on dry, black, curled and twisted leaves. Var. re- 

 pandum G. Lister, not rare in Europe, has not been reported 

 from North America. 



2. Didymium quitense (Pat.) Torrend, Fl. Myx. 150. 1909. 

 Chondrioderma quitense Pat.; Pat. & Lag. Bull. Soc. Myc. Fr. 11: 212. 1895. 



Plasmodium? Sporangia scattered, sessile, hemispherical, 

 depressed, 0.4 to 0.5 mm. diam., or forming long plasmodiocarps, 

 smooth, white; outer sporangial wall of small lime-crystals com- 

 bined to form a white, eggshell-like crust, separating from the 

 membranous, pale purplish, inner layer. Capillitium a network 



