250 THE MYXOMYCETES 



4. Dianema Rex 



Proc. Acad. Nat. Sc. Phila. 1891 : 397. 



Sporangia simple or plasmodiocarpous; capillitium composed of 

 threads without noteworthy thickenings, running entirely across the 

 sporangium, attached both to the base and to the opposite wall, not 

 joined to form a network. 



KEY TO THE SPECIES OF DIANEMA 



a. Spores free b 



a. Spores clustered d 



b. Sporangia sessile or substipitate 1. D. andersonii 



b. More or less plasmodiocarpous c 



c. Pulvinate; dull red or iridescent; spores 8-10 /i 2. D. harveyi 



c. Broadly expanded; gray-brown; spores 6-9 /x 3. D. depressum 



d. Wall cartilaginous, opaque; on wood 4. D. corticatum 



d. Wall membranous, translucent; on lichens and hepatics. ... 5. D. repens 



1. Dianema andersonii Morgan 



in Macbride, N. A. Slime-Moulds ed. 2. 239. 1922. 

 (as D. andersoni) 



Sporangia globose, sessile or substipitate, 0.6-0.8 mm. in diameter, 

 seated on a thin brownish hypothallus, the wall a thin surface some- 

 what thickened below and brownish at the base; capillitium arising 

 out of the thickened base, the threads hyaline or pinkish, ascending, 

 nexuous, simple, or branched a time or two, the extremities attached 

 on all sides to the wall of the sporangium; spores free, globose, very 

 minutely warted, pale, pinkish, 10-12 /*. 



This species differs from D. harveyi Rex in the sporangiate rather 

 than pulvinate or plasmodiocarpous fructification, and the uniform 

 pinkish color of the wall and of the spores; the capillitial threads 

 show occasional minute roundish tubercles as in Didymium; the spores 

 are somewhat larger than in D. harveyi. Miss Lister, in the third 

 edition of the English monograph, suggests that this is the same 

 as Lamprodermopsis nivalis Meylan, which she transfers to Dia- 

 nema. Careful comparison of the type specimen of D. andersonii 

 with an authentic specimen of the Lamprodermopsis, communicated 

 by Dr. Meylan, does not seem to support this view. The wall of the 

 Dianema is rather densely charged with granular material while that 

 of the Lamprodermopsis is thin and translucent. The capillitium of 

 the former is scanty, slender and sparsely branched, and does not 

 vary greatly in thickness, but the threads are united at the base as 

 is usual in the genus; the capillitium of the latter is abundant, robust 

 at the base, branching profusely, the ultimate branchlets being as 





