32 H. L. Russell. 



CONCLUSIONS. 



For sake of convenience, a short review of the points which have 

 been developed in the preceding pages will now be made. 



1. The increasing importance of the bacterial portion of phyto- 

 pathology necessitates a more thorough investigation of the influence 

 of bacterial life in general upon plant-tissue than has heretofore been 

 considered necessary. 



2. The artificial inoculation of higher plants with different micro- 

 organisms (not known to be pathogenic for plants) reveals the fact, 

 contrary to the usually accepted idea, that quite a goodly number of 

 different species are able to withstand the action of the living plant 

 organism for a not inconsiderable length of time. 



3a. Of the species which are able to live in plant-tissues for a con- 

 siderable period of time, those which are ordinarily adapted to a 

 saprophytic method of existence are particularly prominent. Not 

 all saprophytes, however, possessed this power, but in certain forms, 

 as B. fluorescens, B. acid, lact., B. butyricus, etc., it was a marked 

 feature. 



36. Among those forms which are facultative parasites upon the 

 animal body, but few were found that seemed to be able to live 

 in plant-tissue. With the exception of B. pyocyaneus and the 

 Schweineseuche bacillus, they gradually decreased in numbers and 

 finally died. 



3c. The inoculation of plants, not taxonomically related to the 

 natural hosts of bacterial plant parasites, with species of micro- 

 organisms naturally parasitic on vegetable tissue, showed that while 

 the bacteria were unable to spread, they could survive at the inocu- 

 lation point in large numbers. 



4. Not only were numbers of different species of bacteria able to 

 live in the plant from 40 to 80 days or more, but many of them 

 (mostly saprophytes) were able to spread throughout the tissue of the 

 plant to a limited extent (20 to 50 mm. or more). 



5. The local distribution always took place in an upward direc- 

 tion, and the bacteria were found to be generally intracellular instead 

 of intercellular. 



6. According to the present views of physiologists regarding the 

 transpiration stream, it does not seem possible that this current can 



