50 



LITERATURE ' 



Duggar (5) states that "wheat in paratFined pots con- 

 taining rich garden loam is practically unaffected by 

 pyridine at the enormous rate of 8,000 parts per million, 

 this solution being used to moisten the soil to 60 percent 

 of its water holding capacity." 



Davidson (3) studied the effect on the growih of 

 wheat of cumarin and vanillin when added to Dun- 

 kirk clay loam. It was found that 180 parts per mil- 

 lion * of cumarin, or 600 parts per million of vanillin 

 depressed the yield somewhat. Davidson concludes 

 that even this effect is on the soil and not on the plant. 



Skinner (28) in pot experiments, found that vanillin 

 added to the soil before potting, at a concentration of 

 500 parts per million, was harmful to wheat plants 

 grown in infertile Florida sandy loam soil and infertile 

 Susquehanna sandj^ loam, but had no effect on wheat 

 grown in fertile Hagerstown loam. Vanillin added to 

 plots of the experiment farm of the Agricultural De- 

 partment at Arlington at the rate of 285 pounds per 

 acre stunted the growth of cow^peas, garden peas and 

 string beans. The same investigator found vanillin 

 present in the soil of these plots six months after its 

 application, and demonstrated by pot experiments that 

 the compound still injuriously affected the growth of 

 plants. 



Fraps (6) has found that vanillin at a concentration 

 of 100 parts per million is injurious to corn or oats 

 in but one of eight soils, but is injurious in all cases 

 at a concentration of 200 parts per million. Cumarin 

 was injurious at 100 parts per million in six out of nine 

 experiments; at 200 parts per million in five out of 

 seven, and at 300 parts per million in one of two. He 

 also found that the vanillin and cumarin rapidly dis- 

 appeared during the course of the experiment. 



Funchess (7) found that pyridine and quinoline in 

 Norfolk sandy loam or Cecil clay in pots had little 

 harmful effects or proved decidedly beneficial to the 

 growth of corn or oats. Vanillin and cumarin had 



^ Only the literature dealing with the effect on plant growth 

 of vanillin, cumarin, pyridine and ciuinoline when added to 

 the soil is cited here. In water culture, according to Schreiner, 

 Reed and Skinner (22), vanillin is harmful to wheat at a con- 

 ceniration of 1 part per million; cumarin, at 1 part per million; 

 pyridine, at 50 parts per million and (luinolinc at 5 parts per 

 million. 



* Expressed in parts per million of air-dry soil. 



