78 Journal of Agricultural Research voi. vi, no. 2 



days to observe the development of cloudiness. In order to be certain, 

 however, of the viability of the organism, loops of bouillon from these 

 tubes were transferred to planted plates of nutrient agar, and the sub- 

 sequent development noted. No growth occurred in the tubes exposed 

 at temperatures above 65° C. 



No attempts have been made to determine the exact degree of tolerance 

 of this organism to acids. When transfers were made to dextrose- 

 peptone agar + 10, + 20, and + 40 Fuller's scale, it was found at the end 

 of three days to have grown in the first two, but growth was completely 

 inhibited in + 40 acid. Hydrochloric and citric acids were employed in 

 acidification. 



The organism seems to exhibit a very considerable resistance to drying. 

 In the desiccation experiments bacteria from vigorous pure cultures on 

 potato plugs were smeared by means of a sterile platinum needle on clean 

 miscroscopic slides in moist chambers. The moist chambers containing 

 the microscopic slides were sterilized prior to transferring the bacterial 

 smear to the slides. These preparations were made on June i , and placed 

 in a wall closet in the laboratory. On July i , August i , and September i 

 several of the microscopic slides were removed from the moist chambers 

 and placed in sterilized Petri dishes, using proper aseptic precautions 

 in making the transfers. Tubes of melted nutrient agar which had been 

 cooled almost to the point of solidification were poured upon these 

 smeared slides. No growth occurred in the case of those tested on 

 September i, but those tested on July i and August i were still alive. 

 From this it is believed that the organism can retain its viability for 

 about two months. 



The group number according to the descriptive chart of the Society of 

 American Bacteriologists is 221.3332513. 



LIFE raSTORY OF THE ORGANISM 



Pseudomonas citri, so far as is known, passes its entire life cycle under 

 natural conditions within the tissues of the host. New infections appear 

 in spr,ing shortly after the new growth has begun. In southern Ala- 

 bama the first appearance of Citrus canker in the field was noted on May 

 II, in 1914, and on May 27, in 1915. Old diseased areas on the foliage 

 together with the cankers on the twigs and larger limbs are undoubtedly 

 the source of infection in the spring. New leaves formed near old twig 

 cankers are especially liable to become diseased first. Infections are not 

 confined to the new growth, however. Old diseased areas on leaves and 

 branches may enlarge by the renewed growth of the organism which has 

 remained dormant on the margin of the old cankers. New cankers may 

 also develop on old foliage and twigs, especially near the old, actively 

 growing cankers. Under favorable conditions new infections may appear 

 at any time throughout the growing season of the host. In one instance 



