Nutrients 99 



214; Geiger-Huber u. Burlet, 1936, 215; Thielman 

 u. Pelece, 1940, 227; Duhamet, 1939, 209), callus 

 cultures from poplar and carrot (Gautheret, 1937, 

 211, 1939, 212, 1940, 213 ; Nobecourt, 1937, 74, 1938, 

 75, 1939, 77), and some other types of plant issue 

 cultures (Fiedler, 1938, 45; Thimann and Skoog, 

 1940, 454) . It has also been shown to be produced 

 by some roots (Thimann, 1936, 228; Nagao, 1936, 

 249, 1937, 250, 1938, 251 ; van Overbeek, 1939, 253 

 254 ; van Overbeek and Bonner, 1938, 255) . There 

 is no evidence that it is necessary for such growth 

 and considerable evidence to show that it may be 

 highly injurious. Ascorbic acid, biotin, and other 

 vitamins may likewise play an as yet undeter- 

 mined role in the development of plant tissues. 

 (Kogl u. Haagen-Smit, 1936, 358; Bonner and 

 Bonner, 1938, 204 ; Duhamet, 1939, 209). 



Organic nitrogen. Amino-acids. Many plant 

 tissues require, in addition to water, salts, carbo- 

 hydrate, and thiamin or other vitamin, some 

 source of organic nitrogen. This may be supplied 

 in a variety of ways. Many plant tissues will 

 thrive on a nutrient in which this need is met by 

 the single amino-acid glycine (glycocoll) (White, 

 1939, 182). This is obtainable as a synthetic prod- 

 uct of high purity and is to be recommended wher- 

 ever its use will give satisfactory results. In 

 other cases, it may be necessary to supply a more 



