Mayi3, i9i8 Some Bacfevial Diseases of Lettuce 381 



much effect on the results of the inoculation experiments as the venti- 

 lation and moisture. 



The inner whorl of leaves was the part of the plant usually infected. 

 No mature closed heads were inoculated, but occasionally in infection- 

 cage experiments some of the older leaves had numerous red speckled 

 areas, which, on examination, proved to be filled with bacteria. 



One of the inoculation tests was made in tvvO greenhouses during the 

 winter when the temperature of one was 8 to 10 degrees lower than that 

 of the other. The plants were placed in infection cages, where there 

 would be little ventilation and high humidity. The disease took readily 

 in both houses. This test was followed up in the summer, when both 

 houses were practically of the same temperature. The plants were 

 grown in open beds, those in one house being set farther apart and kept 

 better ventilated than the other one. The plants of both houses were 

 inoculated by spraying them wath the same cultures. The infection 

 produced in the vv'ell-ventilated house was almost negligible, while the 

 usual blackened margins of the inner rosette of leaves occurred on the 

 close-set plants in the poorly ventilated greenhouse. The organism was 

 reisolated from the diseased margins, and on inoculating with the colo- 

 nies so obtained, the disease was again produced. 



This disease of lettuce need not be confused with the browning of 

 margins of lettuce leaves due to tipbum, or sunscald, for the brown of 

 tipbum is a much lighter color. 



The hearts of young and old celery plants were inoculated with the 

 Kansas organism by spraying, also by smearing the bacterial slime on 

 the leaves and then puncturing them. No infection followed on either 

 young or old plants. 



DESCRIPTION OF THE KAXc5AS ORGANISM 



The organism is a bacterium motile by means of polar flagella, one or 

 two at each pole, a few noted \\dth three at a pole Casares-Gil's flagella 

 stain, (PI. 41, E). It is a short rod rounded at the ends, occurring in 

 short chains or singly. Stained with carbol fuchsin in the leaf it is 

 0.83 to 1.66 IX long and 0.83 to 1.25 fx. wide, the majority being 1.45 /xlong 

 and 0.83 ix wide. Grown on beef agar for 24 hours and stained with 

 gentian -violet, it is 0.83 to 1.87 fx long and 0.42 to 0.83 fx vride. Stained 

 with carbol fuchsin, same age, it is 1.25 to 2.08 (x long and 0.42 to 0.83 fx 

 wide. 



Capsules were stained by Ribbert's capsule stain (PI. 41, D). 



Endospores are not produced. Tests were made by boiling several 

 liquid cultures of different ages for 3 minutes; also heating others to 

 80° C. for 20 minutes. Transfers were made in each case before and 

 after boiling. Before heating and boiling all cultures were alive, as 

 growth took place in the transfers, but none took place in transfers made 

 from cultures after they had been boiled or heated. The organism forms 



