TOXICITY OF GALACTOSE AND MANNOSE FOR GREEN PLANTS 437 
however, is fermented with greater difficulty, and it is suggested 
(Armstrong, 1912) that perhaps a different mechanism is involved in 
its fermentation. Mannose has a common enolic form with glucose 
and fructose, and any one of the three may be converted into any other 
under the influence of alkalies. It is therefore all the more surprising 
to find mannose behaving similarly to galactose and not like glucose. 
In a previous paper it was suggested that the toxicity of galactose 
might be due to its oxidation products. The first oxidation products 
of glucose and galactose are gluconic and galactonic acids. Various 
cultures were made with Canada field pea in which the effect of calcium 
galactate and calcium gluconate was to be noted. The experiments 
were made as were those previously described. In no case was any 
injurious action of calcium galactate noted. 
It is not yet possible to offer any explanation accounting for the 
toxicity of the two sugars. An explanation of antagonism is suggested 
by the phenomenon commonly observed with fungi, namely, the 
election of organic substances, whereby if two organic substances are 
offered only one may be absorbed. Various cases of this nature have 
been reported even for stereoisomeric compounds. According to this 
view, in a mixture of glucose and galactose, the toxicity of the latter 
would be prevented because of the absorption of glucose and the 
nonabsorption of galactose, and a similar condition would hold for a 
mixture of saccharose and galactose. The failure of the other sugars 
to antagonize the toxicity of galactose would be due to their inability 
to prevent the absorption of the galactose. Work is being continued 
on this subject. 
REFERENCES 
Armstrong, E. Franklin. The Simple Carbohydrates and the Glucosides, pp. 72-76. 
1912. 
Knudson, Lewis. Toxicity of Galactose for Certain of the Higher Plants, Annals 
of the Missouri Bot. Garden 2: 659-666. 1915. 
Influence of Certain Carbohydrates on Green Plants. Cornell Univ. Agr. 
Expt. Sta. Mem. 9: 1-75. 1916. 
Wilson, J. K. Calcium Hypochlorite as a Seed Sterilizer. Amer, Journ. Bot. 2: 
420-427. 1915. 
