﻿DECAY AND SOIL TOXINS 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 213 

 George B. Rigg 

 The decomposition products of a specific plant organ and their 

 effects on the growth of other plants furnished the point of attack 

 for the work on toxicity reported in this paper. The material 

 used was the rhizomes of Nymphaea advena Ait. and N. polysepala 

 Greene. This material was obtained at intervals from July 19 12 

 to October 1915, at various places in the vicinity of Chicago, 

 Illinois, and Seattle, Washington. 



Review of literature 



RELATED WORK ON TOXICITY 



The organic constituents of soils have been under investigation 

 by workers in' the United States Bureau of Soils for 10 years. 

 Livingston (12, 13) found toxic substances, probably organic, 

 in an unproductive soil. Schreiner (21) and his co-workers have 

 isolated from soils more than 25 organic compounds differing widely 

 in chemical character. Some of these (for example, dihydroxy- 

 stearic acid) have proved harmful to growing plants; some (for 

 example, nucleic acid) have been found beneficial; and some have 

 not been shown to have any effect on the growth of plants. Bot- 

 tomly (3) has found that certain aerobic organisms grow well 

 in peat and form from it compounds that are beneficial to the growth 

 of plants. He suggests that very small amounts of accessory 

 organic substances may be necessary for the growth of plants. 



Humic acid has been much discussed as a possible factor in 

 plant growth. Not only the effects of this so-called humic acid, 

 but also the constitution and nature of the substance are in doubt. 

 Schreiner (21) regards it as a mixture of substances. Wieler (29) 

 takes the view that humic acids in soils are inorganic acids result- 

 ing, for example, from the chemical decomposition of salts. 



Bauman and Gully (2) have suggested that the acidity of bog 

 water is due to the fact that the cell colloids of the disintegrating 

 295] [Botanical Gazette, vol. 61 



