178 ^ ROYAL SOCIETY OF CANADA 



The swellings in the roots of this and other plants of tliis series 

 were not bacterial nodules, and bacteria were not found in their cells 

 as long as the plants remained alive. The outer tissues of the nodose 

 parts of the roots were ruptured, especially the longitudinal walls of 

 the cells which separated, exposing the inner tissue as columnar chains 

 of cells. The bacteria which contaminated the cultures had to some 

 extent lodged in these open spaces of the ruptured tissue, but their 

 position here appeared to be only accidental. (See photographs 38 

 and 39). 



Flash IV, not inoculated. — The plant began to decline after March 

 11th as if from nitrogen starvation, and by May 31st there was only 

 a little life remaining. No bacterial colonies formed, but the roots 

 became very nodose because of the internal swelling and rupture of 

 the tissues. The flask was examined October lOth. There was a small 

 bacillus present in great numbers and invading the decaying tissues 

 of the root and stem. The bacilli were mostly joined end to end in 

 pairs and did not resemble Fs. radicicola. 



Flash VI, not inoculated. — No bacterial nodules appeared on the 

 roots as long as the flask was observed until October 19th. The roots 

 became nodose because of a swelling and rupture of the tissues. There 

 were some living shoots up to September 25th. On October 19th the 

 roots only appeared to be alive. On examination of the roots Fs. radi- 

 cicola was not to be found. 



Flash X, containing two pea seeds was inoculated September 12th, 

 1905, with a culture obtained from a nodule on Pisum sativum, which 

 had been grown on artificial media one year and 199 days. 



On December 12th, 1905, there was no bacteria visible in the 

 medium, which was blue with the litmus, except just beneath the seed, 

 there the medium had become acid. One of the plants had formed 

 no roots and it afterwards died without forming any roots. The other 

 plant had a stem 5 cm. long and a root 1 cm. long on December 12th. 



The plant which lived had eight nodules February 11th, 1906, 

 and 35 nodules on March 23rd. By May 7th there were 80 nodules. 

 (See photograph 40, Flask 2, taken February 20th, which illustrates 

 this flask culture). 



On March 23rd, the only evident contamination was one mould 

 colony. On that date the roots were vigorous, forming a closely tangled 

 mass between the glass and the agar. The nodules were all small and 

 almost round. The total weight on April 23rd was 430 grams, that 

 is, there was a loss of 20 grams in 121 days, or less than .2 gram per 

 day. At that rate the 250 grams of medium in the flask would have 

 been exhausted in 1,250 days, or three years, five months. 



