TOXICITY OF GALACTOSE AND MANNOSE FOR GREEN PLANTS 435 
periments previously described with galactose. It was found that 
mannose at a concentration of 0.025 mol. behaved very much as did 
galactose, with the possible exception that the browning of the roots 
was not so intense as with galactose. The same general effect, 
however, was noted as is evident in Figs. 3 and 4. 
Fig. 3. I. Galactose .025 mof. 
2. Mannose .025 " 
3. Mannose .025 " + galactose .025 mol, 
4. Mannose .025 " + glucose .025 " 
5. Pfeffer's solution. No sugar. 
Antagonistic Action. — Since glucose and saccharose had been found 
to antidote effectively galactose, these two sugars were tested with 
respect to their preventing the toxicity of mannose. Test-tube cul- 
tures were used as for the galactose experiments, the amount of the 
medium being 25 cc. Both peas and wheat were used. The cultures 
were permitted to grow for two weeks, and the data were then re- 
corded. All cultures were in duplicate, and those for pea, with the 
exception of the cultures containing saccharose, were repeated. 
The cultures employed were as follows: 
