3 84 



BOTANICAL GAZETTE 



[may 



oxidation which occurs in poorly drained soils, where putrefactive 

 processes are known to exist. In investigating this question, two 

 crops of wheat seedlings were grown in Arlington clay loam in paraf- 

 fined wire pots, giving the pots different amounts of water. 



Lot I of the pots was kept at the optimum water content of the 

 soil. The soil in lot II was kept saturated with water from the start, 

 and the soil in lot III was saturated after the wheat seedlings were 

 up. The relative green weight of the first crop of wheat plants, which 



March 



8, was: 



ioo 



rop, grown from March 17 to April 

 II, 67; III, 116. Extracts of these soils were then 

 made and wheat plants were grown eleven days in the various extracts. 

 At the end of that time the growth and oxidizing power of the plants 

 in the different solutions were determined with the result shown in 



Table XII. 





TABLE XII 



Growth and oxidation in extracts of soils of varying moisture content 

 expressed in terms of relative transpiration. 



Growth 



No. 



1 

 2 



3 



Soil treatments 



Soil kept at optimum 



Soil kept at saturation 



Soil saturated after plants were up 



100 



78 

 151 



IOO 



69 



II 



effects 



ondi- 



more 



! marked upon oxidation than upon 



wuiia appeal ikj uc lllU^il lliuit men iv^v.i ^.^^^ ~ , 



growth. The soil, which was kept at optimum and only satura 

 after the plants had started, seemed to remain favorable to grow 

 in the pots and in the extracts, but its extract was plainly not a\<>^ 

 able to oxidation. In regard to the increase of growth, it sho 

 remembered that this lot of soil was alternately very wet an . 

 during the course of the experiment. 



EFFECT OF TOXIC COMPOUNDS UPON OXIDATIO 



Aside from the foregoing experiments, in which there 

 extracts of soils which displayed toxic qualities toward p an* 



used 



compo 



few investigations were made upon the action of organic 

 whose toxic properties had been previously determined. 

 The organic compounds employed for this purpose wer 



nilHn 



> 







