igi6l RIGG—SOIL TOXI.XS 299 



afterward exposed to the air until the odor of ether disappeared. 

 It was then allowed to decay in redistilled water. The liquid 

 resulting from this decay was strained through cheesecloth and 

 diluted with redistilled water to 1600 cc. 



Solution 3B. — The juice squeezed out in preparing solution 

 4A was extracted by shaking with an equal volume of ether in a 

 separator)- funnel, which was then freed from ether by heating 

 to 40 C, and subjecting to suction (2 cm. of mercury) by means 

 of an aspirator for 24 hours. This, when diluted 1600 cc, consti- 

 tuted solution 3B. 



Solution jC. — The ether used in extracting 3A was combined 

 with that used in extracting 3B. This was allowed to evaporate 

 spontaneously and as much of the residue as possible was taken 

 up in 1600 cc. of redistilled water at 40 C. 



Preparation 3D. — The solid matter remaining on the cheese- 

 cloth in the preparation of 3A was air-dried and ground with an 

 equal volume of sand to form a soil. 



Solution 4A. — This was the water extract of the fresh rhizome 

 made under sterile conditions. The rhizome was cut into small 

 pieces and placed in flasks with water. These flasks were stoppered 

 with cotton and sterilized in an autoclave. This solution stood 

 sterile for n months before its toxicity was tested. 



Solution 5A. — This was the water solution of the ash from the 

 fresh rhizome. 



All sand used in the previous preparations and in the follow- 

 ing experiments was either no. 2§ quartz or "Ottawa test." In 

 all cases it was washed in 10 per cent HC1, freed from acid by 

 washing in running water, and Anally rinsed with redistilled water. 



The "Knop's solution" had the following composition: 1 part 

 KN0 3 ; 1 part KLtPO,; 1 part Mg S0 4 ; 4 parts Ca(N0 3 ) 2 . This 

 was made up to o. 1 per cent. 



Where "tap water" is mentioned, the water used was Chicago 

 city water. Where "Cedar River water" is mentioned, the water 

 used was Seattle city water, which is piped from the river near 

 its origin in a snow- fed lake. Where "Lake Washington water" 

 is mentioned, the water is that supplied from Lake Washington 

 to the botany laboratories at the University of Washington. 



