1915] 



KNUDSON — TOXICITY OF GALACTOSE 663 



tures made in triplicate. The seeds germinated in four days 

 and even by this time in the higher concentrations of galac- 

 tose, browning of the cotyledons was becoming evident. This 

 browning of the cotyledons intensified with time and at the 

 end of 20 days the peas in the 1 per cent and 2 per cent 

 galactose cultures showed marked discoloration, and death of 

 roots soon occurred. The height of tops was also markedly 

 affected in the presence of galactose of a concentration of 1 

 per cent or over. (See pi. 22 fig. 4.) The above experiments 

 were repeated with wheat and corn and the results secured 

 were similar. 



Antagonistic action of glucose toward toxicity of galactose. 



It was noted previously that raffinose and lactose are 

 utilized by Canada field pea, and this has been verified by 

 other experiments. The use of lactose by vetch has also been 

 decidedly shown by experiments not yet reported. Since both 

 lactose and raffinose are assimilated by pea and vetch, and 

 since it is highly probable, as previously suggested, that these 

 sugars are hydrolyzed before assimilation, it is possible that 

 the glucose and levulose exercise a protective action against 

 the galactose. 



An experiment was made to test the hypothesis with respect 

 to glucose. Test-tube cultures were prepared as in the pre- 

 vious experiment, but in this case were made in quadrupli- 

 cate. One series contained 1 per cent glucose plus 1 per cent 

 galactose and the second series contained 1 per cent galactose 

 alone. The plants were grown for 25 days in the greenhouse 

 and the general results are clearly evident in pi. 22 figs. 2 

 and 3. In the case of the 1 per cent galactose culture the pri- 

 mary roots were killed, but with the 1 per cent glucose added, 

 the primary root tip was killed and the epidermis and part 

 of the cortex, but the inner part of the root was not appar- 

 ently injured, for secondary roots developed which seemed to 

 be more resistant to the toxic action of the galactose, for these 

 root tips suffered no injury and not even a browning of the 

 root was secured as was the case with the primary root (pi. 22 

 fig. 3). The experiment was repeated a second time and the 

 results secured are concordant with the first. 



