[Vol. 2, 191f.J 



664 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



Discussion. — So far as the writer has been able to discover, 

 previous mention has been made of the toxic nature of 



galactose for plants. Molliard 1 , however, intimates that 



alactose is toxic for radish, for unlike other sugars, the 

 alactose permitted no development beyond a 5 per cent con- 



sm 



on and with 2 per cent galactose the plants a 

 He concludes that galactose is not utilized by 



r> 



That galactose is injurious to the green plants employed 

 is definitely shown. It does not appear to be toxic to fungi 

 since Aspergillus niger, several species of Penicillium, a 

 species of Fusarium, and a species of Mucor were all found 

 growing in cultures which became contaminated. It is defin- 

 itely known also that certain yeasts are able to ferment galac- 

 tose. The character of the injury effected by the galactose 

 in the above experiment and the method of action have not 

 yet been determined. Incidental observations indicate that 

 the galactose on penetrating kills the cells in its path. In the 

 case of peas grown on 1 per cent galactose the peripheral 

 layers of the cotyledon showed the original starch reserve 



sted. In the presence of glucose it was only the epi- 

 dermis and part of the cortex which suffered injury. It would 



that the outer layers of cells were injured before suffi- 

 cient ducose had accumulated to render them resistant to the 



ction of galactose, or perhaps the penetrability of the 



inner cells for galactose was altered by the presence of glu- 

 cose. In what manner the glucose antidotes the toxicity of 

 galactose cannot yet be stated. It may be possible that it is 

 the oxidation products of galactose that are the injurious 

 agents and that the glucose prevents the formation, or modifies 

 the character, of the oxidation products and that the toxicity 

 is thereby overcome. Investigation into other phases is in 

 progress. 



1 Molliard, Marin. Action morpliogenique <le quelques substances organiques 

 sur les vegetaux superieurs. Rev. G6n. de Bot. 19: p. 331. 1907. 



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