Nutrients 95 



1922, 57 ; Robbins and Maneval, 1923, 59 ; Robbins 

 and V. B. White, 1937, 178; Malyschev, 1933, 53, 

 54; White, 1932, 63, 1940, 172, 173). Mannose, 

 galactose, etc., have also been tested. There is 

 some evidence that galactose may be quite toxic 

 (White, 1940, 173). This unsatisfactory behavior 

 of the monosaccharides may be due in part to the 

 difficulty in purifying them adequately (Robbins 

 and Bartley, 1937, 170; Robbins and Schmidt, 

 1939, 61). All commercial preparations of mono- 

 saccharides, even the best ' ' C.P. Grade, ' ' contain 

 varying amounts of impurities which may be in- 

 jurious. They are also relatively unstable to heat 

 and cannot be autoclaved with impunity (Thiel- 

 man, 1938, 171). Fortunately, the much more 

 easily purified and more stable disaccharide, su- 

 crose, is a completely satisfactory carbohydrate for 

 all plant tissues which have so far been grown suc- 

 cessfully (White, 1934, et seq., 65, 66, 78, 172, 173; 

 Fiedler, 1936, 45; Robbins and Bartley, 1937, 222; 

 Robbins and Schmidt, 1938, 60; Thielman, 1938, 

 171). Although maltose, brown sugar (Robbins 

 and Schmidt, 1938, 60, 1939, 224), and even dextrin 

 (White, 1940, 173) have given excellent results in 

 some experiments, their beneficial effects above 

 those of sucrose are to be attributed to non-car- 

 bohydrate impurities. There is to date no evi- 

 dence that any sugar other than sucrose needs 



