DiDYMIUM 127 



that developed under preferred conditions of environment, and 

 there is Httle difficulty in separating them. It is possible that 

 they are variations of the same general form, similar to the 

 numerous variations found in D. squamulosum and D. melano- 

 spermum, but they are convenient centers, much more so than 

 any variations of the two latter species, among which it is difficult 

 to find a combination of characters that are uniform and constant. 



13. Didymium squamulosum (Alb. & Schw.) Fries, Symb. Gast. 

 19. 1818. 



Diderma squamulosum Alb. & Schw. Consp. Fung. 88. 1805. 



Plasmodium colorless (Lister). Sporangia gregarious, sub- 

 globose or hemispherical, umbilicate beneath, 0.5 to 1 mm. diam., 

 stalked, sessile, or forming effused, pulvinate or netted plasmo- 

 diocarps, either white from abundant stellate crystals of Hme, 

 which often form a wrinkled, deciduous, scaly, outer crust, or 

 gray when the lime-deposits are scanty; in the plasmodiocarp 

 forms the crystals often sparsely distributed; sporangial wall 

 membranous, sometimes mottled with red-brown towards the 

 base, at length breaking into small fragments. Stalk white or 

 pale yellow, rarely orange, cylindrical, deeply furrowed, rough 

 with deposits of lime in minute crystals in the wall, varying much 

 in length, usually spreading at the base into a white, discoid 

 hypothallus. Columella large or small, white or yellowish, hemi- 

 spherical, absent in effused plasmodiocarps. Capillitium vari- 

 able, of slender or coarse threads, either almost simple or 

 branching at acute angles, colorless, violet, or purplish brown, 

 often with dark calyciform thickenings. Spores violet-brown, 

 8-11 (JL diam., faintly or distinctly spinulose, the spinules often 

 grouped in clusters. (Plate 15, fig. 6.) 



Type locality: Germany. 



Habitat: On dead leaves, herbaceous stalks, etc. 



Distribution: Common and abundant throughout North 

 America. 



Illustration: Lister, Mycetozoa ed. 3. pi. 109. 



This common and abundant species often has large colonies 

 spreading widely over piles of decaying vegetable matter. It is 

 very variable, and some of the phases arc often seen on different 

 parts of the same general habitat. The lime on the wall may be 

 densely or sparsely distributed, smooth or wrinkled. The stalk. 



