1912.] 



New Bacterial Disease of Pisum sativum. 



173 



into the cells. There the nucleus is often attacked, the cytoplasm destroyed, 

 and the cells collapse, thus forming rents in the tissues. 



There is considerable evidence to show that the bacillus passes up the 

 plant through the tissues above mentioned, through the funicle, and probably 

 the micropyle into the young developing seed. If one pea is diseased all 

 the other peas in the same pod are diseased to an equal extent. The disease 

 is chiefly spread by the seed, but fresh infection may take place through 

 the soil. 



Inoculation experiments were carried out in the open, but little stress can 

 be laid on the results, as the disease was so prevalent throughout the 

 experimental plot. Pea plants grown in heated soil in boxes, and 

 inoculated just above the ground, when the plants were about 1 foot in 

 height, showed no disease, whereas, in the open, seven out of ten inoculations 

 on the stem just below the youngest .unfolding leaf were successful. 



Further inoculation experiments are necessary, but the above results tend 

 to show that the bacillus can only penetrate very young tissue. This is 

 supported by the fact that large numbers of the bacilli have been found in 

 the inner tissues of the radicle when only about half an inch long. 



Further investigations are in progress. 



In many respects the symptoms resemble those of the formidable disease 

 of sweet pea (Lathyrus odoratus) known as " streak." This disease has been 

 held to be due to Thielavia basicola, but, in view of these observations, that 

 conclusion seems very doubtful, and I may add that, in the stem of diseased 

 sweet peas, I have already found bacteria like those here described. 



