LEAF-SPOT OF COTTON! CULTURAL CHARACTERS 335 



peptone bouillon, nitrate bouillon, Cohn's solution, Uschinsky's 

 solution, Fermi's solution, litmus milk, peptone water in fer- 

 mentation tubes with various pure sugars and alcohols. Com- 

 pare with No. II and No. VIII. 



Non-nutritional Environment. — What is the optimum tem- 

 perature for growth? the maximum? the minimum? Can 

 you get any growth at 1°C. or at 37°C.? Compare critically 

 with No. VIII. Effect of sunlight (try first a 2-minute exposure 

 on a bright day) ? Effect of dry air (use 2-day peptone-bouillon 

 cultures spread on thin sterile cover-glasses — begin at 6 hours; 



Fig. 257. — Spatulate, finger-like out-growths of a gelatin colony of Bacterium 

 malvacearum. 



thereafter drop some of the infected covers into suitable bouillon 

 every 6 hours — Keep covers in a dark place). Effect of freezing? 

 of weak acids? of sodium hydrate? of chloroform in bouillon? 

 Maximum toleration of sodium chlorid in bouillon? Length of 

 time organism will remain alive inside of leaf-spots, or boll- 

 spots? or in cotton stems? It is a very considerable period. 

 For the disease. Signs. — How soon does the disease 

 appear on the inoculated (sprayed or smeared) leaves? How 

 soon on punctured bolls or stems? How soon do the spots 

 change from translucent to brown? Are leaves or bolls com- 

 monly thrown off as a result of infection ? Inoculate very young 



