liY R. GREIG SMITH. 



41 



ture, grow rapidly, and clog the vessels, on account of which tlie 

 plant is unable to obtain its food supplies, and soon succumbs. 



One point to be decided was the influence of salts upon the 

 growth of the bacterium, and to test this matter a faintly acid 

 medium containing peptone 0-5%, dextrose 10%, agar 2%, was 

 prepared, and about one-quarter of a gramme of salt was added to 

 each 10 c.c. 



The Influence of Salts. 



This experiment shows that(l) the bacterium has a preference 

 for phosphate and is indifferent to the other acid radicles ; (2) 

 the acid potassium phosphate, on account of its acidity, checked 

 the growth; (3) potassium may be replaced by calcium, magnesium 

 or ammonium ; (4) sodium is a distinct poison. 



The Poisonous Action of Common 8alt. 



After noting the poisonous action of sodium salts, the idea 

 naturally suggests itself that common salt might be advantageous 

 in checking the gummosis of the cane. Common salt, however, 

 is a poison for most of the higher plants, and might injure the 

 sugar-cane if used in doses sufficiently great to inhibit the 

 growth of the bacterium. On enquiry, I find that healthy crops 

 of cane are grown in Fiji upon soil containing anything under 

 1% of common salt, although when this amount is exceeded t h 



