September 22, 1916] 



SCIENCE 



433 



rye and spelt organisms all behave alike as to 

 pathogenicity when inoculated on wheat, rye, 

 spelt, barley and oats in that they each infect 

 all these grains except oats. A blade blight of 

 oats quite different in type from the blights of 

 the other grains noted above has also been 

 found in Wisconsin and its bacterial cause de- 

 termined. This disease apparently corresponds 

 in appearance with the bacterial blade blight 

 of oats described by Manns. 1 From it a mono- 

 trichous white organism has been isolated 

 which in pure culture infects oats readily but 

 apparently is not pathogenic on the other 

 cereals listed above. 



The detailed account of the studies upon 

 barley blight together with the technical de- 

 scription of that organism as a new species has 

 already been sent to press. The results of the 

 comparative studies on these other bacterial 

 grain blights will be given in a subsequent 

 publication. L. E. Jones, 



A. G. Johnson, 

 C. S. Eeddy 

 University of Wisconsin 



certain bacteria for B. typhosus, one of us 

 (W. D. F.) used and described a method 

 called by us the " double-plate method." 2 This 

 method enabled us to see and photograph the 

 effect which certain bacteria had in limiting 

 or preventing the growth of B. typhosus. 

 The method consisted of dividing a petri dish 

 in halves by means of a small rod or tube and 

 flooding one half of this double-plate with 

 sterile agar and the other with agar contain- 

 ing the antibiont. Over the surfaces of both 

 halves the other antibiont was streaked. The 

 resulting growth of the streaks readily showed 

 the effect of the antagonism. 



Some eight years later, Churchman 3 de- 

 scribes an identical procedure for demonstrat- 

 ing the selective action of gentian violet. He 

 makes no mention of our method but substi- 

 tutes a metal strip for the glass rod and the 

 name " divided plate " for double-plate. He 

 was evidently not aware of our previous de- 

 scription. 



Eecently we have used this method for deter- 



Eig. 1. Aspergillus growing on potato agar. 

 The lower half contains oil of nutmeg (1: 200) 

 which inhibits growth of mold. 



Fig. 2. Penicillium on potato agar. Marked in- 

 hibition due to eugenol (1: 1,000) in lower half of 

 dish. 



ANOTHER USE OF THE DOUBLE-PLATE 

 METHOD 1 



In a study of the antagonism exhibited by 



i Manns, T. E., "The Blade Blight of Oats; a 

 Bacterial Disease," Ohio Agr. Exp. Sta. Bull., 210, 

 pp. 91-167, 1909. 



i Bead at the meeting of the Society of Amer- 

 ican Bacteriologists, TJrbana, 111., December 28- 



30, 1915. Publication authorized by the Director 

 of the Wisconsin Experiment Station. 



- Frost, W. D., ' ' The Antagonism Exhibited by 

 Certain Saprophytic Bacteria Against the Bacillus 

 typhosus Gaffky, " Jour. Inf. Bis., November 5, 

 1904, pp. 599-641. 



3 Churchman, ' ' The Selective Bactericidal Ac- 

 tion of Gentian Violet, ' ' Jour. Exp. Med., Vol. 16, 

 1912, pp. 221-247. 



