I 



Studies of Bacillus Radicicola of Canada Field Pea 27 



Results 

 Nodules developed only in the nitrate-free solution. The plants in 

 most of the solutions in this experiment and in experiment 5 did not grow- 

 well and normally. It is possible that slightly different results might 

 have been obtained had the length of time of the experiment been extended. 

 It was observed, however, in these and in the other experiments, that the 

 number and the size of the nodules on a plant are influenced by the rate 

 and the amount of growth of the plant. In other w^ords, any disturbing 

 factor in the normal functions of a plant tends to hinder the development 

 of nodules. 



experiment 7 



influence of moisture 

 In experiments 7, 8, and 9, the plants were grown in glass tumblers. 

 In each tumbler was placed 300 grams of air-dry sandy soil containing less 

 than 0.5 per cent of moisture. The following percentages of moisture 

 were used: 5, 10, 15, 20, 25, 30, 40, 50, and 60, the percentage being based 

 on the air-dry soil. Three tumblers were used for each percentage of 

 moisture, and five plants were gro'wn in each tumbler. The plants were 

 kept in the greenhouse. They were watered every other day, the neces- 

 sary amount of water to be added being determined by weighing. The 

 soil is naturally well inoculated wdth the Canada field pea organism, but 

 in addition to this each tumbler was inoculated with a pure culture of the 

 organism. The duration of the experiment was four weeks. 



Results 

 The best growth took place in 15, 20, and 25 per cent of moisture. 

 In 5 and 10 per cent of moisture the plants grew very slowly, w^hile in 50 

 and 60 per cent the roots rotted. Nodules were present on all the plants. 

 The number of the nodules on each plant increased with the percentage 

 of moisture up to 40 per cent. These results agree with those of Gain 

 (1893), who found that a larger number of nodules develop when the 

 plants are abundantly watered. 



EXPERIMENT 8 

 INFLUENCE OF CERTAIN SUBSTANCES IN VARYING QUANTITIES 



The same soil and the same kind of vessels were used in this experiment 

 as in experiment 7. Three hundred grams of the air-dry soil was in- 



