Influence of Certain Carbohydrates on Green Plants 61 



effected when the concentration of glucose is equivalent to that of the 

 galactose. When the glucose is still further decreased it is practically 

 ineffective in exerting a protective action against the galactose. These 

 results were confirmed by a second experiment similar to that just described. 

 In the second experiment, however (Fig. 11), better antagonism resulted 

 in the culture having equimolecular solutions of glucose and galactose. 



This toxicity of galactose has been discussed before by the writer 

 (Knudson, 1915) and, as there stated, no previous mention concerning 

 it has come to the writer's notice. Molliard (1907) mentioned the non- 

 availability of galactose for radish. Lubimenko (1906, a and b) reports no 

 injury for Pinus Pinea. Meyer (1886), and later E. Laurent (1887), found 

 that leaves and cuttings of certain plants placed in solutions of galactose 

 absorbed the sugar, producing out of it starch. Most of the deamylated 

 plants used by Meyer, however, did not produce starch when supplied with 

 galactose, although glucose did cause starch production. It may be that 

 the sugar itself is not toxic but that its oxidation products are injurious. 

 The antagonistic action of glucose in this case might operate to render the 

 cell impermeable to the galactose or alter the metabolic products of 

 galactose. If the galactose, for example, could be transformed into 

 starch or some other storage product — a possibility indicated by the work 

 of Meyer and of E, Laurent — then its injurious action might be averted. 

 The presence of a readily available sugar such as glucose might conceivably 

 protect the galactose against oxidation and result in a transformation of 

 the galactose into a storage product such as starch. It is of interest to 

 note here that galactose may be utilized by many fungi and that it is 

 fermented by certain yeasts. Further work on this interesting subject 

 is now in progress. 



SECRETION OF ENZYMES BY ROOTS 



It has already been noted (page 12) that J. Laurent (1904) found inver- 

 sion of saccharose when it was present in the culture medium, and this 

 inversion was ascribed to the action of the invertase secreted by the 

 roots of corn or of peas. Starch was likewise transformed, but this -yv^as 

 ascribed to the action of diastase that had been secreted from the seed. 

 Maze (1899) reported a very marked inversion of saccharose in the culture 

 medium when corn was employed, although in 1911 he reported contra- 

 dictory results. Wohllebe (1911), investigating the secretion of diastase 



