Ethel M. Doidge 417 



13. 4. 20. Numerous minute, water-soaked points on younger leaves: tissues on 

 examination prove to be full of bacteria. 



17. 4. 20. On Datura plant inoculated, organism has produced very numerous 

 spots about 1 mm. diameter and somewhat angular, these are brown and membranous 

 in centre and have a water-soaked margin: these brown spots show a tendency, 

 especially in the younger leaves, to break away and cause a shot-hole effect. Control 

 plant is healthy and shows a sign of infection; replated organism from infected 

 leaves and found it identical with original. 



D. 



7. 4. 20. One plant of Solanum incanum inoculated without wounding. 

 17. 4. 20. No signs of infection on this or later date; leaf is protected by thick 

 covering of hairs. 



E. 



7. 4. 20. One plant of Solanum nigrum, inoculated without wounding. 



13. 4. 20. Slight indications of infection on younger leaves. 



17. 4. 20. Infected spots have developed considerably, but are still small: they 

 are irregular in outline, 1 mm. diameter or up to 2 mm. long, and are light brown 

 and membranous in the centre. Replated organism and found it identical with 

 original. Control plant showed no sign of infection. 



F. 



24. 7. 20. A number of sweet pea plants were inoculated by needle pricks in the 

 stem. The result was entirely negative. 



Description of the Causal Organism. 

 A. Morphological Characters. 



When taken direct from the tissues of the host the organism is very- 

 variable in size and form : the majority are rather stout rods with rounded 

 ends, but some are so short as to resemble coccus forms. They vary 

 from -6 to 4/x in length, and from -5 to -75 fj, in breadth. The majority 

 are 1-1-5 x -6--7/x. 



In young agar cultures (24 hours at 30° C.) the organism is a rod 

 with rounded ends, occurring singly or in pairs, or less frequently in 

 short chains of three to seven elements. The rods are for the most part 

 fairly even in size, measuring 1-1-5 x -6— 7/x; the extremes observed 

 were -8-3x-6--7^. In old cultures they are less regular, and short 

 forms are numerous. 



In young bouillon cultures the rods are similar in form. The organism 

 grows rather reluctantly in neutral bouillon, and in six days old cultures 

 in this medium there are numerous straight or curved rods 4 and 5fj. 

 long and also long undivided threads up to 50 fi long. 



