90 KANSAS UNIVERSITY SCIENCE BULLETIN. 



No. 588 folded filter for the purpose. The residue soils on the 

 filter were washed with sufficient distilled water to make the 

 filtrates up to 1000 cc. These were invariably clear, golden 

 straw in color, and to all appearances would invariably be 

 mistaken for ordinary bouillon. The extracts were then 

 sterilized. 



Five hundred cc. portions were then placed in pint Mason 

 jars (a hydrometer cylinder being, however, a far more satis- 

 factory container) . In these were placed the paraffin blocks 

 containing the plant seedlings. (Plate XXIII.) (The latter 

 were secured in essentially the same manner as that employed 

 by the Bureau of Soils.) The water cultures thus prepared 

 were placed in the greenhouse to permit the growth of the 

 plants. The water lost by evaporation and transpiration was 

 restored in the form of sterile, distilled water. 



All cultures were thus identical in every respect with the 

 exception that different organisms had grown in the samples 

 of soil from which the extracts had been made. Thus in the 

 first series a field soil was employed. Of this 1000-gram por- 

 tions were sterilized and then inoculated according to the 

 following scheme : 



1. Yellow ammonifier. 



2. Ps. radicicola (garden pea). 



3. Azotobacter. 



4. B. prodigiosus. 



5. B. liquefaciens fluorescens. 



6. Cladothrix odorifera. 



7. Aspergillus niger. 



8. Sterilized soil. 



9. Normal soil. 



10. B. subtilis. 



After 14 days' incubation, extracts of the respective soils 

 were made according to method outlined above. These were 

 then employed as nutrient solutions for the growth of wheat 

 seedlings. The results are perhaps best apparent from Plate 

 XXIV, which shows the condition of the seedlings after 18 days 

 of growth. One observes a wide difference particularly in the 

 root development of the seedlings in the various extracts. A 

 most extensive root development occurred in the case of the 

 extracts from the ammonifier, azotobacter and B. liquefaciens 

 fluorescens. 1-3-5. (Plate XXIV.) In contrast to these, the 



