THE EFFECT OF PREVIOUS VEGETATION 



343 



the end of three weeks the plants in the good soil extract were 

 twice as large as those in the extract of the soil which had prev- 

 iously grown sesame and in which cabbages had failed. 



In this experiment a portion of the extract of the sesame soil 

 was shaken up with very finely divided carbon black, which is a 

 good absorber. The solution was then filtered free of carbon 

 black and used as a culture solution for cabbage plants. The 

 plants grew much better in this carbon treated solution, which 

 indicates that the carbon black absorbed from the soil solution 

 something which was harmful to cabbage plants. 



In order to determine if the solution of this soil which had 

 grown sesame was haraiful to other crops, wheat plants were 

 grown. The wheat plants made very good growth. The soil ex- 

 tract showed no indication of being a poor culture for wheat 

 seedlings. The carbon-treated extract grew plants about equal 

 in vigor to those in the untreated soil solution. There was no 

 improvement in growth. These facts point to the presence of 

 some inhibitive material affecting cabbages but not wheat. 



By an examination in the laboratory an oily body, which has 

 a semi-solid appearance when cooled, was extracted from the se- 

 same soil. The amount of material did not permit of purifjdng 

 to any great extent, nor was the soil sample sufficient for further 

 chemical work, but culture experiments were made with the lim- 

 ited amount of material in order to determine what effect it 

 would have on cabbage plants and the interesting observations 

 made therewith are here given. 



The oily body was separated from the soil by extracting it 

 with hot alcohol. About fifteen pounds of soil were used. The 

 alcohol was evaporated lea^nng a residue, which was purified by 

 extracting with petroleum ether. Some oily material was se- 

 cured, which is partly soluble in water. 



The fact of the occurrence of an oily body in soil in which se- 

 same had grown is interesting in connection with the nature of 

 the sesame plant. The seed produced from the sesame plant 

 jneld an oil in amounts of about half their weight. Large quan- 

 tities of the oil-of-sesame are used in the manufacture of soap 

 and oleomargarine, and for other purposes similar to those in 



