306 BOTANICAL GAZETTE [april 



A solution was prepared from each of the following substances, 

 by allowing a quantity of it to decay in redistilled water: potato, 

 turnip, rhizome of Castilia odorata, and rhizome of Typha latifolia. 

 These solutions approximated the strength of solution iA prepared 

 from Nymphaea. They all proved toxic to Tradescantia cuttings, 

 but to a less degree than iA did. Their toxicity was in the order 

 named. 



Discussion 



It is evident from the data given that even very dilute solu- 

 tions of the products of the decay of Nymphaea rhizomes are toxic 

 to Tradescantia cuttings in water cultures and the seedlings of 

 tomato, alfalfa, and corn in sand cultures. 



Although the products of the decay of the subterranean parts 

 of other plants proved toxic, the toxicity of the products of the 

 decay of Nymphaea rhizomes was considerably greater than that 

 of any other plant parts experimented on. While it is possible 

 that toxicity from decay is rather common, Nymphaea seems to 

 merit particular attention in this regard. The dilution of solution 

 iA that entirely inhibited the formation of root hairs on Trades- 

 cantia cuttings contained in each cc. the products of the decay of 

 47mg. of fresh rhizome. Since only 12 per cent of the fresh 

 rhizome is solid matter, the amount of solid whose decay con- 

 tributed to the solutions in each cc. of the toxic solution was 

 o . 56 mg. 



The fact that the solutions listed in table I were all acid, and 

 that their toxicity was largely destroyed by neutralization with 

 sodium hydrate, would seem to suggest acidity as a large factor 

 in the toxicity. The toxicity is not proportional to the acidity 

 as determined by the titration method. It may be proportional, 

 however, to the H ion concentration, or some other factor may be 

 effective. The fact that the toxicity of iA, iB, iC, and 2A when 

 undiluted was not reduced by neutralization with sodium hydrate 

 seems to emphasize further the presence of some other factor. It 

 is possible that the osmotic pressure of such a concentrated solu- 

 tion was high enough to cause injury, although it has been shown 

 elsewhere (20) that this is not the cause of the toxicity of the very 

 dilute solutions. Antagonistic action on permeability might also 



