55 



CoMPAR.vTivE Effect on Plant Growth of Toxins in 

 Sterile and Inoculated Soil. 



In each of 30 two-liter bottles 500 grams of air dry 

 soil were placed. This soil came from the ammonium 

 sulfate manured plots, referred to above. Ninety cc. 

 of tap water were added to each of the bottles. To six 

 of the bottles 0.5 gm. of vanillin was added and to six 

 others 0.5 gm. of cumarin. The 30 bottles were plugged 

 with cotton and sterilized in an autoclave for 3 hours 

 at 15 ll)s. pi-cssure. After sterilization 0.5 cc. of pyridine 

 was added to () of the bottles and 0.5 cc. of quinoline 

 to G others. These compounds were added by means 

 of sterile pipettes. The remaining six bottles received 

 no treatment. Half, 3, of each set was inoculated by- 

 adding about 2 cc. of a suspension of normal soil in 

 sterilewater and all were incubated in a dark cupboard 

 at room temperature for 57 days. At the end of that 

 time ten wheat grains, sterilized by Wilson's method 

 (31) were dropped into each bottle. Sixteen days after 

 planting the wheat the sterile bottles were tested for 

 sterility by plating some of the soil in Brown's albumen 

 agar. AH were sterile save one of the quinoline series 

 which contained fungi. At the same time the wheat 

 plants were removed from the bottles and the tops and 

 roots measured. Due to the ditficulty in removing the 

 plants from the narrow necked bottles considerable of 

 the roots was lost in all cases in which they had pene- 

 trated the soil. The results are given in Table III. 

 The method used in growing the plants and the results 

 with the set treated with pyridine are shown in Plate 

 I, figure 1. 



T.\BLE III. Growth of Wheat in Sterile and Inoculated 

 Soil Which Had Been Incubated for 57 Days. 



From the data it is evident that inoculating the un- 

 treated steamed soil with an infusion from normal soil 



