BACTERIAL DISEASES OF PLANTS 



275 



stomata and lodge in the intra-cellular' spaces under natural 

 conditions. He argues that the bacteria can derive no nutri- 

 ment from the material contained in the spaces between the 

 cells, and therefore cannot produce any disease in the plant. 

 He holds the opinion that pathogenic bacteria cannot dis- 

 solve the cellulose wall of the plant cell. Furthermore, the 

 statement is made that the only spores which can possibly 

 germinate in the aqueous material f v 

 in the intra-cellular spaces are those %, jjjj^^Vj- 

 of the parasitic fungi (Hyphomy- \&&. V^i ^xlv.:V 



'"- : \ * ". '' '; '".-'.- ''-iLj'- ''' .- '' '".'-( 



cetes, etc.), since they possess re- 

 serve food material. These fungi, 

 it is claimed, may dissolve away the 

 cell wall, penetrate the cell with the 

 hyphae, and thus produce a morbid 

 condition therein (rusts, etc.). 



Fischer and some others think 

 that the bacterial infection of the 

 plant is secondary to infection by 

 fungi. He states that the unin- 

 jured plant is impermeable to the 

 attacks of bacteria, and that even 

 in the injured plant only those cells which are attacked by 

 the hyphomycetes, etc., are available for bacterial action. 

 The fact that bacteria are present in diseased plants in 

 enormous numbers is, of course, recognized, but Fischer and 

 others think that they are existing only metatrophically. 



FIG. 52. Cross section of turnip 

 leaf inoculated with Bact. cam- 

 pestre. (Pure culture inocula- 

 tion with needle.) After Smith. 



