96 J ourtial oj Agricultural Research voi. xiii, no. a 



RHIZOCTONIA 

 Rhizoctonia solani Kiihn. 



Identified five times from Idaho soils, twice from group A, once from 

 sample i, and twice from sample 3. Considerable difficulty was expe- 

 rienced in placing this organism in pure culture. This was accomplished 

 but once, in one isolation from group A. The identification was made 

 certain by a careful comparison with authentic cultures of R. solani. 

 The other four identifications were made by a careful study of the 

 mycelial and sclerotial characters, though the fungus was mixed in 

 culture with other fungi, principally species of Fusarium. 



Habitat: R. solani Kiihn. has been reported from a great number of 

 hosts, including the potato, from the soil and from decaying vegetable 

 matter in the soil in humid regions. Cause of russet-scab of the potato 

 and reported to be the cause of other potato disorders, including potato- 

 rosette, aerial tubers, stemblight, damping-off of young potato plants, 

 etc. Cause of damping-off of many economic plants. A complete host 

 index is too long to be included here. A host index and historical sketch 

 was published in 191 6 in a work by Peltier (7), who isolated the organism 

 from Illinois soils. The writer has identified the organism from the 

 roots of alfalfa (Medicago saliva), sagebrush {Ariemesia tridentata) and 

 rabbit-brush (Chrysothamnus graveolens) in southern Idaho. Isolated 

 five times from Idaho soils. 



STEMPHYUUM 



Two species of the genus Stemphylium were isolated, as follows: 

 Siemphylium pirijorme Bos., isolated three times from group A; and 

 Stemphylium paxianum V. Szabo., isolated once each from groups A 

 and B. Identified by Mr. Zundel. 



THAMNIDIUM 



Thamnidium elegans Link., isolated once each from samples 2 and 3. 

 Identified by Mr. Zundel. 



TRICHODERMA 



Four forms of the genus Trichoderma were isolated as follows : Twice 

 from group C and once each from^ samples i and 2. (See statement by 

 Dr. Thorn, p. 93.) Identified by Dr. Charles Thom. 



TORULA 



One species of the genus Torula was isolated, once from group B and 

 once each from samples 1,2, and 3. This species is briefly described as 

 follows : 



Hyphae dark, olivaceous, black in mass, septate; conidiophores simple; 

 conidia in chains, unicellular, subglobose to ellipsoidal, olivaceous, black 

 in mass, 8 to 15 by 6 to 8 ju. 



