BY R. GREIG-SMITH. 819 



stance. It was clearly brought from the soil-particles below, and 

 deposited upon the surface. Experiments were made with a 

 solution of agricere in chloroform, and it was found that when 

 the chloroform was poured over fragments of unglazed porce- 

 lain, the solvent, in evaporating, left the wax upon the upper 

 surfaces or points of the porcelain. A solution of pitch in chloro- 

 form was poured over sand contained in a watch-glass. The 

 solvent evaporated, leaving the pitch as a black film cementing 

 the surface-grains together. Under the film, the sand-granules 

 were light in colour and loose. The great bulk of the pitch had 

 been carried to the surface. Large pieces of unglazed porcelain 

 were saturated with the pitch in chloroform, and hung up to dry. 

 The pieces dried with black surfaces, and, when broken across, 

 white centres were revealed. 



This may be considered to be what happens when the soil is 

 treated with a solvent. The agricere is carried to the surface of 

 the soil -particles or to the surface of the soil, according to the 

 quantity of solvent used. The water-proofing of the particles 

 being destroyed, the nutritive material is dissolved by the soil- 

 water, and is then capable of being absorbed by plants, either 

 immediately or after its conversion into an available form by 

 bacteria. 



The following four sets of experiments have a bearing upon 

 the redistribution and behaviour of the soil-wax. Each of the sets 

 a, b, c and d were made upon different days, and probably had 

 different periods of incubation. In a and h the 20 gm. tests 

 were treated with 5 c.c. of Bac. prodigiosus suspension, of such 

 concentration that there were added 6,400,000 and 8,600,000 

 bacteria, lespectively, per gram of soil. From a general survey 

 of the results, however, I believed that too many bacteria had 

 been added, and that the increases were too near the maximum 

 attainable. In c and d, therefore, a smaller number, 46,000 and 

 47,000, respectively, per gm., were added, in the hope of obtain- 

 ing more divergent figures. The soil was a garden-soil that had 

 been stored for about a month. 



