2 H. L. Russdl 



Fliigge 1 states that bacteria almost never attack higher plants, 

 giving as an only exception Wakker's hyacinth-disease. The low 

 temperature of plants and the chemical composition of vegetable 

 juices he regards as very unfavorable for the development of bacteria, 

 more especially as the cell-juices almost always possess a distinct 

 acid reaction, and thus protect the plant against these micro- 

 organisms, which are so sensitive in this respect. 



Hartig,in the recent edition of his Lehrbuch der Baumkrankheiten 

 (p. 37), also urges the view that the acid reaction of plants prevents 

 the growth and development of bacteria, and that they play a very 

 unimportant role in the production of plant-disease. In the hyacinth- 

 disease above referred to, he says the bacteria do not attack sound, 

 well-ripened bulbs under normal conditions,but only when the tissues 

 have been more or less injured by wounds or previous attacks of fungi. 



He notices, also, BurrilPs claim that the pear-blight is caused by 

 a specific bacillus, but is somewhat skeptical that the form referred 

 to is anything but a secondary accompaniment of the malady. 



DeBary is inclined to support the general views advanced by 

 Hartig, but in his last edition of Die Bakterien (S. 36) he states that 

 it might be possible for bacteria to gain access, through stomata, into 

 the tissues of higher plants, but that this is probable is yet undeter- 

 mined and needs further investigation. 



These observers, all of them recognized authorities in the realm of 

 pathology, seem to regard it as quite improbable that bacteria have 

 any important bearing upon the production of plant-disease. Whether 

 this unanimity of expression is due to the actual absence of bacterial 

 plant-maladies in Europe generally, or because investigations have 

 not been directed in these channels, can only be inferred. 



In consideration of the fact that this branch of vegetable pathology 

 is of increasing importance, and that the reasons assigned for the 

 apparent exemption of plant-tissues from the attacks of micro-organ- 

 isms have been largely based upon the general law known in regard 

 to bacterial life in general, it was deemed advisable that a series of 

 investigations should be carried out with different micro-organisms, 

 to see what effect contact with the living plant-tissues would have 

 upon them; so, at the suggestion of Prof. Welch, this topic was taken 

 up for consideration. 



1 Die Mikroorganismen, S. 515. 



