THE SORGHUM BLIGHT 



215 



the red-blotclied leaves and leaf-sheatlis. The latter are 

 particularly spotted at the upper portion, just below the 

 ligule. If they are stripped from the stalk the carmine 

 coloration is seen to be conspicuously brilliant inside, 

 and often extending over a large area of the interior sur- 

 face of the sheath. On the leayes themselves the spots 

 are usually more numerous along the mid-yeins. The 

 stalks are usually not locally affected until late in the 

 season, when they, too, show evidence of the disease by 

 the appearance of red or rusty spots. On the ^' brush'' 

 of broomcorn similar discolored patches are to be ob- 

 served, and these directly injure the j^roduct. The 

 rusty, corroded places may be frequently found on tlie 

 brush of the manufactured brooms. 



'•The diseased roots also turn red but soon decay, 

 and, of course, lose the bright color. The oldest roots 

 die first, and, as new ones are successively emitted from 

 the base of the stem in the order commonly occurring in 

 these plants, they, in turn, become successively affected 

 and perish. This is why the plant juelds to so slight a 

 23all, while healthy ones resist a vigorous effort. Upon 

 close examination it is evident that the exterior part of 

 the roots or cortex is the 2:)ortion in which the disease is 

 resident, the woody fibers of the interior remaining for a 

 long time unchanged, except throtigh natural decay 

 after the death of the whole root. Btit the woody part 

 is stained from contact with the external layer." 



It has been conclusively shown, both by Professor 

 Burrill, and by Messrs. Kellerman and Swingle, that 

 this disease is due to a distinct species of bacteria, re- 

 quiring a high microscopic power to be seen, and special 

 skill and training to be successfully studied. TVhen 

 highly magnified these bacteria bear a general resem- 

 blance to Fig. 87.. 



Treatment. — Eotation of crops seems to be the 

 l)est method of ^^I'O^'cttting the development of this dis- 



