THE FUNGI WHICH CAUSE PLANT DISEASE 659 



Mycelia-Sterilia (p. 479) 



Numerous forms are known merely as sterile mycelia. They 

 may or may not make sclerotia. In several instances these sterile 

 forms are so aggressive as to warrant classing them among the 

 worst of plant pathogens. Until more is known of them it becomes 

 necessary to arrange and name them, for convenience of reference, 

 in a purely artificial manner. 



Key to form Genera or Mycelia-Sterilia. 



Tubercle-like 



Tubercles connected with fibrils. ... 1. Rhizoctonia, p. 659. 



Tubercles without fibrils 



Cortex discrete 2. Acinula. 



Cortex not discrete 3. Sclerotium, p. 660. 



Maculiform 



Black stromata in leaves and stems 4. Ectostroma. 



Pseudo stromata in cortex 5. Phellomyces. 



Root-like 

 Filaments rigid, broad, terete or depressed, 



dark, white within 6. Rbizomorpha. 



Filaments rigid, capilliform, dark, closely 



adhering 7. Capillaria. 



Cla variform; filaments terete, vertical, sim- 

 ple or branched 8. Anthina. 



Cobwebby or byssoid 

 Cespitose interwoven, primary hyphse 



jouied in bundles 9. Ozonium, p. 661. 



Cespitose interwoven, hyphae not fascicu- 

 late, black 10. Rhacodium. 



Cobwebby, soft, evanescent, white or pale 11. Hypha. 

 Adpressed, creeping, dendritic, white to 

 brownish, not forming a continuous 



membrane 12. Himantia. 



Membrane-like; densely interwoven, form- 

 ing a continuous suberose or coriaceous 

 membrane 13. Xylostroma, p. 663. 



Rhizoctonia De CandoUe 

 Sclerotia variable in form, homy-fleshy; cortex thin, mem- 



