1915] 



DUGGAR RHIZOCTONIA CROCORUM AND R. SOLANI 437 



fact that when fleshy root crops of this type are attacked by 

 such fungi they die gradually, while herbaceous plants (cot- 

 ton, alfalfa, etc.) wilt suddenly. This is probably closely re- 

 lated to the effect of the fungus on the conducting tissues. 

 In the beet root the invaded tissues are pale brown, and often 

 cracks or rifts occur, though rotting may take place without 

 such lesions. Sometimes there is partial recovery after the 

 cracks are formed, and in this case callous tissue is developed. 

 A soft crown rot of the radish induced by this fungus has 

 apparently been reported only once (Duggar and Stewart, 

 '01). A similar disease of the carrot was found in 1900 in 

 New York and this is possibly the disease first reported by 

 Kuhn ('58, pp. 241-243), although he did not identify it as 

 due to a Rhizoctonia. 



STEM AND HOOT ROTS OF HERBACEOUS PLANTS 



Rhizoctonia Solani produces serious stem and root rots of 

 a number of economic herbaceous plants, among which the 

 following are known to be important: carnation (Dianthus 

 caryophyllus), Sweet William (Dianthus barbatus), bean 

 (Phaseolus vulgaris), sweet-pea (Lathy rus odoratus), and 

 violet (Viola odorata). 



The carnation stem rot is one of the most destructive dis- 

 eases occurring on this host and is wide-spread in the United 

 States. The general symptoms of the disease on carnation 

 and Sweet William are much the same. The stem is affected 

 at or just below the soil level. The fungus penetrates and 

 kills the cortex which may be readily slipped from the wood. 

 Through the medullary rays the hyphae also enter the pith, 

 which likewise decays. In later stages of the disease the 

 wood shreds, due to the complete penetration by the fungus 

 of all parenchymatic tissues. 



Several important epidemics of Rhizoctonia on bean have 

 been reported from different parts of the United States. In 

 addition to the outbreak described by Duggar and Stewart 

 ('01), Hedgcock ('04), a few years later, found the bean dis- 

 ease severe near St. Louis. The base of the stem and the 

 larger roots bore characteristic ulcerations; pods were af- 



