100 EXDOSPOREAE [DIDERMA 



a. Spores reticulated. 1. D. subdictyospermum 



b. Spores not reticulated — 



a. Sporangia white — 



Sporangia disc-shaped, stalked. 



2. D. hemisphericum 



Plasmodiocarps flat ; columella brownish flesh- 

 coloured. 3. D. effusum 



Sporangia hemispherical ; columella white, convex ; 

 inner sporangium-wall rarely persistent ; spores 

 violet-brown, 7-10 jx. 4. D. spumarioides 



Sporangia subglobose ; columella small, convex, 

 white ; outer sporangium- wall shell-like, separating 

 from the persistent colourless inner wall ; spores 

 purplish-brown, 11-14 /x. 5. D.globosum 



Sporangia subglobose or ovoid (or forming plas- 

 modiocarps in subsp. deplanatum) ; columella sub- 

 globose or clavate, orange, red-brown, or pale, 

 absent in plasmodiocarp forms ; inner wall 

 persistent, orange below ; spores purplish-brown, 

 9-14 jx. 6. D. niveum 



b. Sporangia flesh-coloured, depressed. 7. D. testaceum 



c. Sporangia reddish clay-coloured or brownish buff ; wall 



single. 8. D. simplex 



Subgenus 2. — Leangium : sporangium-wall cartilaginous.* 



a. Sporangium-wall brown externally, white and crystalline 



on the inner side ; columella often absent. 



11. D. Trevelyani 



b. Sporangium-w r all without a crystalline layer — 



a. Spores with widely scattered warts ; sporangia stalked. 



12. D. floriforme 



b. Spores closely spinulose or nearly smooth — 



Sporangia pinkish-brown, sessile, subglobose; 

 columella indefinite ; capillitium usually colour- 

 less. 9. D. Sauteri 



Sporangia ochraceous, sessile, subglobose or ring- 

 shaped ; columella indefinite ; capillitium purple- 

 brown. 10. D. ochraceum 



Sporangia white, grey or brown ; columella pale, 

 hemispherical ; stalk stout, ochraceous. 



13. D. radiatum 



* Sporangium-wall as in Eudiderma in the white forms of D. radiatum. 



