34 Plant Tissue Culture 



76, 1939, 77; Nobecourt and Dusseau, 1938, 311), 

 and with White's (Fig. 12) independent work in 

 America, these studies have led to the first really 

 successful prolonged cultivation of undifferenti- 

 ated plant tissues (White, 1939, 78, 333) . At about 

 the same time that Gautheret's work was initiated, 

 the author of this volume, under the influence of Dr. 

 and Mrs. Warren H. Lewis and of the late Profes- 

 sor Duncan S. Johnson, began at the Johns Hopkins 

 University an intensive study of the whole prob- 

 lem of plant tissue cultures. The methods of ap- 

 proach finally adopted as most promising, al- 

 though developed independently, came to resem- 

 ble superficially those of Kotte and Bobbins on the 

 one hand and of Gautheret on the other (White, 

 1931, 32, 1932, 63, 89, 1933, 64, 116, 141, 142). 

 These studies led in 1934 to the first prolonged 

 cultivation of excised roots (White, 1934, 65), to 

 the development of satisfactory synthetic culture 

 media in 1937 (White, 1937, 141, 143, 144, 180, 181, 

 231, 1939, 182, 1940, 172, 173, 232), and to the pro- 

 longed cultivation of undifferentiated plant tis- 

 sues in 1939 (White, 1939, 78). The work of Bon- 

 ner (Bonner, 1937, 198, 1938, 199, 1940, 201; Bon- 

 ner and Addicott, 1937, 42), Fiedler (1936, 45), 

 Galligar (1934, 46, 1936, 166, 1938, 167, 1939, 47), 

 Marotto (1935, 55, 1936, 56), Loo and Loo (1935, 

 216, 1936, 217), and others, and recent studies of 



