DISEASE RESIST.\NCE IN PL.^NTS. 129 



succeeded in developing resistant strains. A similar disease in 

 North Carolina has been investigated in the same way with very 

 favorable results. 



This plant is also attacked by Nematode worms, which cause 

 gall-like swellings on the roots. Experiments are now underway 

 by officials of the U. S. Dept. of Agriculture for the selection of 

 varieties resistant to this trouble. 



Cotton. 



Very satisfactory results have been secured in selecting varieties 

 resistant to the wilt of cotton in the South. The work has been 

 carried on by W. A. Orton of the Department of Agriculture. He 

 has found that several varieties of Eg^-jDtian cotton, as well as one 

 upland cotton, give great promise of resistance. He suggests 

 crossing the different resistant sorts, especially resistant varieties 

 of different races, with the hope of obtaining varieties which will 

 combine the good qualities of both races. INIr. Orton's investiga- 

 tion of cottons resistant to the wilt fungus revealed a very important 

 fact. He found that even with the most resistant sorts grown on 

 infected land, infection occurred in the rootlets but the fungus was 

 not able to gain entrance to the main root system, and therefore, 

 could not spread in the plant. The resistance, then, in cotton to 

 the wilt fungus is not caused by some peculiarity of the roots which 

 prevent the entrance of the fungus into the tissue, but to some 

 undetermined character which prevents the spread of the fungus 

 to any extent after it has gained entrance to the tissues. 



Watermelon. 



An account has already been given of the success of Mr. Orton 

 in obtaining a wilt resistant variety of the watermelon by hybridiza- 

 tion with the citron. 



