i9o8] SCHREINER &• REED— TOXIC PIANT CONSTITUENTS 93 



its chemical composition is unknowii, but it is probably a toxalbumen. 

 BoKORXY ('96) found that ricin is slightly toxic to algae and infusoria. 

 On account of its slight solubility, we were not able to make tests of 

 solutions having a concentration greater than 50 ppm. The wheat 

 plants were somewhat injured by concentrations of 50 and 40 ppm. 

 Mucin is also comparatively insoluble in water and hence a wide 

 range of concentrations could not be employed. In a saturated solu- 

 tion there was practically no growth of the roots of the wheat plants. 

 In a solution of 100 ppm., which is slightly below the point of satura- 

 tion, the plants were seriously injured in the growth of both roots and 

 tops. A solution contaming 5 ppm. was slightly stimulating to the 



growth of wheat plants. 



Quinic acid, which occurs in cinchona bark associated with the 

 alkaloid qumin, proved to be quite toxic to seedlings. In all except 

 the more dilute solutions, qumic acid was xQiy toxic to wlieat plants. 



1000 



and 500 ppm. were dead; in 100 ppm. only the roots were dead. In 

 concentrations below 50 ppm. the plants were as good as the controls 

 grown in distilled water; and in the solutions containing 5 ppm. there 

 was a slight stimulation of gro'^th. 



Discussion and suinmarj 



nn 



nxmiber of the compounds occur- 

 fT^^fc l^r^nr^ wheat seedliners. The 



toxicity of certain compounds appears to be greater for plants than 

 for animals ; in the case of other compounds the reverse relations seem 



exist 



The amino-acid compounds display a relatively low toxicity, and 

 some of them appear to serve directly as nutrients to the plants. 

 Two exceptions desenx mention. TjTosin, which was found to 

 cause injury in concentrations of 25 to 10 ppm., may be regarded 

 as oxyphenylalanin. Reference to the table shows that alanin itself 

 was sH^tly injurious in the highest concentrations, and it is easy to 

 understand that increased toxicity should follow the mtroduction of 

 the oxTphenvl group. Aspartic acid is the other amino-compound 

 which di3pla^'s relatively great toxicity to the plants. Aspartic acid 

 differs chemicaUv from the other amino-compounds employed m 



