conspectus: how infection occurs 



15 



how infection occurs 



As I have already described elsewhere how infection oc- 

 curs, '^ I will dwell on it here only for a moment, offering a few 

 examples. 



The commonest way of infection is probably through wounds. 

 In Italy, the olive tubercle due to Bacterium savastanoi has 

 been observed to begin very often in wounds made by hail- 



FiG. S. Fig. 9. 



Fig. 8. — ^A beef peptone gelatin ( + 10) stab culture of Bacterium lachrymans 

 after 12 days at 20°C. In the unliquefied part the colonies along the needle track 

 are very small showing that it is aerobic. 



Fig. 9. — Two different illuminations of a small gelatin colony of Bacterium 

 lachrymans to show the characteristic margin. X 14. 



stones. In South Africa, crown gall is said to be disseminated 

 in the same way. In this country and also in Sumatra, Bac- 

 terium solanacearum enters the plant more often than other- 

 wise through broken roots. A tomato or tobacco plant with 



1 Smith, Erwin F.: "Bacteria in relation to plant diseases," Carnegie Inst. 

 Washington, Publ. 27, Vol. 2, pp. 51-64, 1911. 



