62 A Bacterial Spot of Cltnis 



been pricked or otherwise slightly wounded. None of the lemons or 

 other citrus fruit which were atomised without wounding developed 

 any spots, but I do not regard this as conclusive evidence that the 

 organism cannot find its way through the stomata, for several reasons. 

 In the first place, the fruit which was used for the experiment had 

 been hanging on the trees in a very dry atmosphere, and the outer 

 tissues of the rind had become comparatively dry and leathery, and 

 it was noticed that even after wounding these infected less readily 

 than those used in the preliminary experiment which were cut after 

 an exceptional spell of rainy weather; also in the first experiment 

 a number of infections appeared on lemons which were injected with 

 a hypodermic syringe at points where no injections had been made, 

 and on naturally infected fruits on many spots w^here no wound can 

 be found, and sections through the tissues show the bacteria in the 

 substomatal cavity, but this will be alluded to later. 



Further inoculations will be necessary before anything conclusive 

 can be arrived at with regard to the possibiUty of stomatal infection, 

 but obviously the most frequent method of infection is through wounds. 



On the trees the spots are only found on ripe fruit, and two or three 

 farmers have reported it as occurring only on fallen fruit or developing 

 in the store room. The organism is very probably a soil bacillus which 

 first invaded fruit lying on the ground and has now taken on a parasitic 

 habit. It was found quite possible to infect green lemons, although 

 the organism attacked them less readily than the ripe fruit. 



The organism loses its virulence rather rapidly on artificial media ; 

 this was clearly shown by inoculating two similar sets of lemons, one 

 with a freshly isolated culture, and the other with a culture isolated 

 about a month previously and transferred fifteen times. On the first, 

 signs of infection were visible after 48 hours and distinct spots in four 

 days ; on the second, the discoloration was much delayed ; it was not 

 visible till the fourth or fifth day and the infected areas comparatively 

 small and poorly developed. 



The identity of the organism in fruit and branch was also tested. 

 A culture of this bacillus isolated from a leaf base infection was used 

 to inoculate a number of sound lemons with positive results. 



A strain isolated from lemons sent from the Constantia Wine Farm 

 produced a few positive infections on some young trees growing in 

 tins in the Laboratory grounds. From these the organism was again 

 isolated and employed with positive results to infect a number of lemons. 



