106 THE^MYXOMYCETES 



e. Capillitium dense, dark; plasmodiocarp very flat; spores 



1 1-14 n 7. D. dubium 



f. Sporangia sessile or nearly so; crust thick, fragile, 



distant 8. D. crustaceum 



f. Typically with distinct stipes g 



g. Peridium usually depressed or lenticular, umbilicate 



below * 



g. Peridium subglobose or globose, not markedly um- 

 bilicate « 



h. Spores irregularly reticulate; stipe often yellowish 



or pinkish 9. D. intermedium 



h. Spores nearly smooth to spiny or warted, but not 



reticulate * 



i. Stipe yellow or orange; peridium cartilaginous, yellow- 

 ish; lime often in scale-like clusters 10. D. leoninum 



i. Stipe pale brown; peridium grayish buff; columella 



yellowish, rough or spiny 11. D. eximium 



i. Stipe white, fluted; fructification sometimes sessile or 



plasmodiocarpous 12. D. squamulosum 



i. Stipe very dark to black j 



j. Sporangia greatly flattened, discoid 13. D. clavus 



j. Less compressed, large, over 0.5 mm. in diameter; 



capillitium dark, coarse 14. D. melanospermum 



j. Smaller; capillitium pale, delicate 15. D. minus 



k. Stipe dark brown to black; columella dark, often nearly 



obsolete 16. D. nigripes 



k. Stipe yellow to yellow-brown; columella white or pallid 17. D. xanthopus 

 I. Sessile or short-stalked; ochraceous or yellowish 



white; columella very large, pulvinate 18. D. vaccinum 



I. Broadly plasmodiocarpous, depressed and very thin; 



peridium tending to break away as a whole 19. D. listeri 



1. Sessile, pulvinate to plasmodiocarpous *» 



m. Spores nearly smooth, 12-14 fx 20. D. dijjorme 



m. Spores very dark, rough, obscurely banded and sub- 

 reticulate, 12-15 /x; peridium diderma-like, the crystals 

 obscure 21. D. quitense 



m. Spores with short spines, often clustered, sometimes 



with reticulate patches, 9-10 ;u 22. D. trachysporum 



1. Didymium nivicolum Meylan 



Bull. Soc. Vaud. Sc. Nat. 57 : 40. 1929. 

 PI. VIII, Fig. 177. 



1925. Didymium wilczekii Meylan ex G. List., Mycetozoa ed. 3. 120, in part. 



Sporangia sessile, subglobose, 1-1.5 mm. broad, or plasmodiocarpous, 

 white; internal layer of peridium very thin, transparent, covered with a 

 more or less pulverulent mass of lime crystals aggregated into concave 

 or discoid scales; capillitium of rather rigid, anastomosing pale purplish 

 to pallid threads, bearing occasional nodules and swellings; columella 



