General Physiology of Plants 199 



it stands today is hardly usable for the latter, for 

 the obvious reason that the basic nutrient for tis- 

 sues is also an excellent nutrient for many of these 

 organisms. It may, of course, be possible to 

 modify the nutrient in such a way as to make it 

 suitable for the host tissue but not for the infect- 

 ing organism. Lewis and McCoy (1933, 301) used 

 a primitive sort of organ-culture technique in the 

 study of bacterial nodule formation on the roots 

 of legumes. Although their results were not en- 

 tirely satisfactory, they suffice to indicate one 

 direction in which the more highly perfected tech- 

 niques may prove useful. Kiker and Berge (1935, 

 317) foresaw some such possibility in connection 

 with their studies of crown gall organisms, as did 

 Nobecourt and Dusseau (1938, 311) and Berthelot 

 and Amoureux (1937, 276). Nothing has been 

 done with fungi except Gioelli's observations on 

 the effects of chance contaminations on his cam- 

 bium cultures (1938, 292). If the roots of cereals 

 can be grown in the same manner as those of dico- 

 tyledonous plants, they should serve as interesting 

 substrata for the study of rust infections. 



Viruses in tissue culture have been studied to a 

 somewhat greater extent than have bacteria and 

 fungi, though still barely enough to give a sugges- 

 tion of the possibilities. Viruses of a consider- 

 able number of diseases of the mosaic group have 



