REPORT OF THb SOCIETY 



121 



Experimental Work To Date. 



Isolations. — Numerous attempts to isolate a causal organism from diseased 

 tissue were made, and in a few cases ■ — the majority being from internal stem 

 lesions — a yellow motile organism was obtained. This was cultured on nutrient 

 and potato agars and in beef bouillon, and the following preliminary inoculation 

 experiments made: 



Series 1. — The organism was inserted, under sterile conditions as far as 

 possible, in a slit in the stem of healthy tomato, potato, tobacco, sweet pea and 

 broad bean plants; the stem carefully wrapped with tin foil, and the plants 

 placed under large bell jars. This experiment was duplicated, and cultures of a 

 yellow organism isolated at different times were also used, but in every case 

 the results were negative. 



Series 2. — The organism was sprayed on healthy tomato, potato, tobacco, 

 sweet pea and broad bean plants, both wounded and unwounded; and as before 

 no disease symptoms were produced. 



Series 3. — The series of experiments tabulated below were carried out 

 by Dr Dickson in 1923; 



From a study of the table, it is interesting to note that, with the exception 

 of plant No. 8, the time between inoculation and the first appearance of symp- 

 toms, is about 10 days. In this connection it might be noted that this is the 

 time taken for tomato mosaic to develop. Also, that the organism used on 

 plants Nos. 3 and 4 was an original culture from necrotic tissue implanted on a 

 nutrient agar slope. First and subsequent subcultures of the yellow organism 

 from this tube failed to produce the disease on healthy tomato plants later. 



Series 4- — In April 1924, the writer inserted diseased tomato tissue into 

 healthy plants of potato, sweet pea and broad bean and covered the wound with 

 tin foil. No positive results were obtained. 



In continuing experiments in the greenhouse this winter it was found that 

 the easiest way to transmit the disease was by rubbing the leaves of healthy 

 plants with crushed tissue of diseased plants. 



