122 THE NORTH AMERICAN SLIME-MOULDS 



Sporangia gregarious, depressed-globose, umbilicate below, whitish 

 or gray, small, about >4 mm., stipitate; stipe erect, rather slender, 

 black, faintly striate, about equal to the sporangium in the horizontal 

 diameter; columella distinct, dark brown, globose or depressed- 

 globose, attaining in some cases the centre, rough ; capillitium delicate, 

 almost colorless, radiating, sparsely branched ; spores in mass dark 

 brown, by transmitted light violet-tinted, minutely roughened, 

 8-10 ti. 



Probably more common than the preceding, and generally mis- 

 taken for it. Distinguished by its smaller size, longer and more 

 slender stem, and general trim, well-differentiated appearance. Cer- 

 tainly very near the preceding, of which Mr. Lister regards it as 

 merely a variety. Professor Morgan thought it in this country the 

 more common form. 



New York, Ohio, Iowa; reported from Europe, Africa, South 

 America. 



9. DiDYMiUM CLAVUS (Alb. & Schw.) Rabenhorst. 



1805. Physarum clavus Alb. & Schw., Consp. Fung., p. 96. 



1829. Didymium melanopus Fries, Syst. Myc, III., p. 114. 



1844. Didymium clavus (Alb. & Schw.) Rabh., Ger. Cr. FL, No. 2282. 



1875. Didymium clavus (Alb. & Schw.) Rost., Mon., p. 153. 



1899. Didymium claims (Alb. & Schw.) Rabenh., Macbr., A^. A. S., p. 90. 



1911. Didymium clavus Rost., List., Mycet., 2nd ed., p. 128. 



Sporangia gregarious, pale gray, discoid or pileate, depressed, stipi- 

 tate; the peridium dark-colored, frosted with calcareous crystals 

 above, naked below; stipe short, slender, tapering upward, furrowed, 

 arising from a hypothallus more or less distinct, black; columella 

 obsolete; capillitium of delicate threads, pale or colorless, little 

 branched ; spores violaceous, pale, nearly smooth, 6-8 /x. 



This species is well differentiated, easy of recognition by reason of 

 its peculiar discoid sporangium, calcareous above, naked and black 

 beneath. D. neglectum Massee, reported from Philadelphia, is said 

 to be a slender form of the present species. The figures of D. clavus 

 by Albertini and Schweinitz are excellent, as also the description. 



Not common. Pennsylvania, Ohio, Iowa. 



