1909.] Bacteria on the Groivth of non- Leguminous Plants. 289 



untreated bulbs was very noticeable during growth, the treated being more 

 vigorous. The treated bulbs, when lifted, were noticeably larger than the 

 untreated. After the bulbs were dry they were carefully weighed, and 

 yielded 



Untreated 69 lb. 3 oz. 



Treated 82 „ 1-| „ 



an increase of 12 lb. 14J oz., or 18 - 6 per cent. 



Experiments on parsnips grown in ordinary garden soil. In January, 

 1908, the ground was deeply dug and given a medium dressing of London 

 dung followed by a dressing of powdered chalk. The seeds were sown early 

 in February in rows running north and south. A fortnight after the north 

 half of each row was watered with a mixed culture of Pseudomonas and 

 Azotobacter. In January, 1909, the roots were harvested, every root being 

 weighed, with the following results : — 



Untreated 68 roots 22 lb. 14 oz. 5 - 38 oz., average per root 



Treated 65 „ 26 „ 10 „ 6"55 „ 



an increase of 21 "7 per cent. 



For the fixation of free nitrogen in laboratory cultures of Pseudomonas 

 and Azotobacter the presence of carbonate of lime in the medium is necessary. 

 In all the above experiments care was taken that a sufficiency of carbonate 

 of lime was present in the soil to enable the bacteria to do their work 

 effectively. 



