1 68 Journal of Agricultural Research voi. xix.No.4 



cultures on injured and uninjured leaves; (5) by root inoculations with- 

 out wounds, using mixtures of the two organisms; and (6) by means of 

 grain aphids. 



He reports that inoculations in the field and in the greenhouse showed 

 that the yellow organism when used alone produced no lesions and that 

 the white organism when used alone produced only "limited and non- 

 typical lesions," which formed slowly, extended from % to i inch from, 

 the point of infection, and then remained checked. When a mixture of 

 the two organisms was used the lesions appeared in from 10 to 12 days 

 and spread rapidly. From these results he concludes that the disea-se 

 is a symbiosis, the white organism requiring the presence of the yellow 

 organism to be actively pathogenic. 



He also states that the virulence and viability of the white organism 

 on artificial culture media depend greatly upon association with tiie 

 yellow organism and that the pathogenic action of the white organism 

 was more marked when carried over winter in mixed culture with the yel- 

 low organism than when carried over separately. After nine months 

 in pure culture t'he white organism failed in several instances to grow. 



Manns sta'tes that endospores cfccur. These were stained with hot 

 carbol fuchsin from 2-months-old cultures. The figure of these spores 

 in his Plate IX is too indistinct to be of any value in verifying his state- 

 ment. 



His white organism is described as a short motile rod with polar 

 flagella. These are three to five times the length of the rods in his 

 Plate IX, fig. 4, and one to six times those in his text figure No. i . The 

 rods measure in the majority of cases 0.75 by 1.5 /x. They are rarely 

 in chains of three to four. 



The thermal death point is 60° C. The optimum temperature is 20° to 

 30°. He states that his organism is pathogenic on oats, corn, timothy, 

 barley, wheat, and bluegrass. 



The group number for his white organism is given as 11 1.2223032. 

 Manns' yellow organism is a bacillus with the group number 222.2223532. 



Manns suggests the probability of the organism's wintering over in the 

 soil and so being distributed to the leaves by spattering rains. He 

 states that there is no doubt that on seedlings lesions sometimes start 

 on the roots or on that part of the stem in contact with the soil. He 

 does not describe these lesions. The possibility that the disease is seed- 

 borne is not mentioned. 



Manns' descriptions of individual lesions are so meager and his descrip- 

 tions of general signs so inclusive as to lead to grave doubt about his hav- 

 ing worked A\'ith a single bacterial disease. There is no doubt, however, 

 that he sometimes had typical halo-blight lesions, because of his Plate 

 XIII, but with this exception there is no conclusive evidence from either 

 his text or figures that he had this disease under observation; and the 



