98 DISEASES OF THE SWEET PEA 



termine soil acidity, based on the use of 

 litmus paper, devised by Mr. J. E. Har- 

 ris,^ who found that some kinds of litmus 

 paper are not suitable. Experiments have 

 shown that Kahlbaum's litmus paper is the 

 best for the purpose. It is so sensitive that 

 it is necessary to leave it in contact with 

 the soil particles only for a moment or two. 

 Soil only very slightly acid will change the 

 litmus paper to a distinctly red color. 

 Acid soils are easily corrected by the use 

 of lime. The latter favors Thielavia rot 

 but this is no consideration where sterilized 

 soil is used. 



RHIZOCTONIA ROOT ROT 



Corticium vagum B. and C. 



No mention is made in literature of a 

 Rhizoctonia disease of sweet peas, al- 



* Harris, J. E., Soil Acidity and Methods for its De- 

 tection. Science. N. S. XL: 491-493, 1914. 



