MVCELIA STERILA 401 



cultures isolated from single spores of manv so-called species of 

 the Sections Elegans and Alartiella. As a result they place 10 

 species, 18 varieties, and 12 forms belonging, according to Rein- 

 king and WoUenweber, to Elegans in one species, Fzisarhnn oxy- 

 sponnn. From Alartiella 5 parasites were placed as forms in F. 

 solani, and 2 species, 3 varieties, and 1 form \\ere placed in Hypo- 

 myces solani, a perithecial fungus. Gibber elk saiibmettii consti- 

 tutes the perithecial stage of F. gramiiieiim, which causes scab 

 on heads of barley, wheat, and other grains. 



AIYCELIA STERILA 



A score of genera and approximately 400 species have at one 

 time or another been included in this non-sporiferous group. 

 Some of them were removed from the group as their fertile stages 

 were discovered. Many of them form sclerotia, which are com- 

 pact structures of definite form, usually light-colored internally 

 but having a dark, hard rind. 



In Sclerotium is included S. roljsii, which is especially destruc- 

 tive to a wide variety of wild and cultivated species in the south- 

 eastern United States. It attacks stems near the soil level. Its 

 basidial stage is Corticium (Hypochnus). Sclerotium oryzae on 

 rice and 5. delphinii on larkspur produce similar types of disease. 



Sclerotiinn bataticola occurs in warm res^ions the \\-orld over, 

 attacking^ the roots of a wide variety of cultivated and wild 

 species. Its sclerotia, which are 15 to 30 1.1 in diameter, form in 

 abundance within the woody tissues. This organism possesses a 

 conidial stage, designated Macrophoviina phaseoU by Ashby 



(1927). 



The wide-spread Rhizoctonia solani causes damping-off of 

 seedlings and stem rot of more mature plants. It has Corticiimi 

 vagiim as its perfect stage but appears as an arachnoid ^^•eft on the 

 basal portion of diseased stems or over the soil surface. This 

 fungus has characteristic coarse, septate hyphae whose lateral 

 branches are constricted at their point of origin; a septum occurs 

 just beyond the constriction in each lateral. Its brown sclerotia 

 form in abundance on potato tubers. 



The Rhizoctonia stage and the sclerotial stage of Corticiinn 

 koleroga, causing thread blights of many species of trees. 



