400 



BACTEEIAL DISEASES OF PLANTS 



50C. (10-cc. portions in thin test tubes 17 mm. in diameter 

 inoculated from young peptone bouillon cultures). Repeated 

 twice in 1920 with same result, following exactly Petri's meth- 

 ods. The checks grew promptly. The 20 heated tubes re- 

 mained clear (20 days). However, 50C. is not the thermal 

 death-point. That is still lower, i.e., between 43C. and 46C. 

 (Miss Brown); over 45C. (Miss Elliot). It grows very slowly 

 below 5C. (Petri). 



FIG. 308. Prof. Luigi Savastano. (Photograph made in Naples at the time he 



was studying olive tubercle.) 



A non-volatile acid is promptly formed from dextrose and 

 galactose and this acid appears to be unfavorable to further 

 growth. Saccharose is, on the contrary, very favorable to 

 growth and less acid reaction is visible when it is used in litmus 

 agar. Air is necessary for the production of acid from dextrose 

 and galactose, i.e., there is no growth or production of this acid 

 in the closed end of such fermentation tubes as yield it in the 

 open end. Lactose or maltose added to litmus agar does not 



