General Physiology of Plants 203 



logical study. Gautheret (1935, 15, 1937, 282, 

 1938, 283, 284, 1940, 286-289), Dauphine (1930, 

 279), Bobbins and bis colleagues (Bobbins and V. 

 B. White, 1936, 62), and Addicott (1941, 196) have 

 utilized root cultures for some anatomical and 

 histological studies. White (1939, 78) Gautheret 

 (1938, 283, 284) and Gioelli (1937, 290) have made 

 a few similar studies with callus cultures. There 

 remains, however, much to be done in this direc- 

 tion. 



Summary 



The tissue culture technique has been applied to 

 the study of the reactions of tissues, organs, and 

 cells to variations in concentrations of nutrient 

 materials, growth stimulants, toxins, and other 

 environmental variables. These reactions can be 

 measured in terms of mass increase, differentia- 

 tion, level of respiratory activity, enzyme or 

 water secretion, tropistic bending, and many other 

 sorts of behavior. Bacteria, molds, and viruses 

 have been cultivated on growing isolated plant 

 organs as hosts and the host behavior studied. 

 These represent some of the fields to which the 

 technique has already been applied. Many more 

 obviously remain as yet untouched. 



