312 13ACTEKIAL DISEASES OF PLANTS 



under which chains and filaments are formed. Involution 

 forms. Under what conditions do they occur? 



Cultural Characters. — ^Behavior on thin-sown agar-poured 

 plates. Ditto in agar-streak cultures and stab cultures. Char- 

 acter of growths on thin-sown gelatin-poured plates. Ditto 

 in stab cultures and streak cultures on gelatin. Growth in 

 streaks on Loffler's solidified blood serum. Behavior on potato. 

 Growth in milk and litmus milk (examine every day). Growth 

 in synthetic media — Cohn's solution, Fermi's solution, Uschin- 

 sky's solution, etc. Action in peptone water on various sugars 

 and alcohols in fermentation tubes. Is any gas produced? 

 Is there ever any clouding of the closed end? Is any acid 

 formed in the open end? Test in appropriate media for pro- 

 duction of indol, ammonia, hydrogen sulphid, amylase, lab 

 ferment, proteolytic ferment. 



Non-nutritional Environment. — Thermal death-point (begin 

 with 45°C.). Maximum temperature for growth (try first in 

 + 15 peptone beef bouillon at 30°C.). Optimum temperature 

 for growth (use measured loops into bouillon and examine every 

 three hours). Lowest temperature at which growth occurs 

 (try first at 1°C. and continue experiment for six weeks). 

 Effect of dry air (using young bouillon cultures first). Effect 

 of insolation (expose on ice to a bright sun for 5 minutes and 

 hold half of each plate covered as a check). Effect of freezing 

 (salt and pounded ice). Behavior in salted bouillons (try 

 5 per cent first) . Behavior in bouillon over chloroform. Tolera- 

 tion of sodium hydroxide in bouillon (begin with — 22) . Tolera- 

 tion of organic acids in bouillon — tartaric, citric, malic, etc. 

 (begin with +30). Action of fungicides. 



For the disease. Signs. — Describe early, middle and 

 late stages of the disease and determine how long it takes to 

 produce these conditions on sprayed plants at given tempera- 

 tures. Make inoculation experiments at the same time in two 

 houses (or places) having temperatures 10 degrees apart: 

 one 20° to 25°C., the other at 30° to 35°C. Are Miss Mc- 

 Culloch's statements as to impossibility of obtaining growth 

 or infections at or above 29°C. entirely correct? In that case, 



