igoS] SCHREINER ^ REED—TOXIC PLANT CONSTITUENTS 8l 



THE ACTION OF SOIIE UREA DERIVATIVES 



Four compounds which are structurally related to urea were 

 studied with regard to their action upon plants. Alloxan and guanidin 

 are sufficiently soluble in water to permit of being used in a concen- 

 tration of ICO ppm. Guanidin was used as guanidin carbonate. 

 Guanin and xanthin are so slightly soluble in water that the highest 

 concentrations used were only 40 and 25 ppm. respectively. 



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KiTA (:o4), who also found that some fungi were unable to utilize 

 guanidin as a source of carbon, although they could utilize it as a source 

 of nitrogen. In our experiments with wheat seedlings a concentra- 

 tion of ICO ppm. of guanidin carbonate was sufficient to kill, and all 

 the lower concentrations employed, including i ppm., caused seri- 

 ous injury. Alloxan, the ureid of mesoxalic acid, was stated by 

 LoEW ('99) to be an unfavorable source of carbon for bacteria. It 

 is quite toxic to wheat, but less toxic than guanidin. Seedlings were 

 killed by solutions containing 1000 ppm., and injured by lower con- 

 centrations down to 100 ppm. Guanin was tested only in concentra- 

 tions of 40, 20, 10, 5, and I ppm. on account of its slight solubility. 

 In all these concentrations there was no harmful effect to be noticed, 

 Xanthin is also so slightly soluble in water that the range of concen- 

 trations employed was small. In concentrations of 25, ro, 5, and i 

 ppm. it was slightly beneficial to the growth of wheat plants. 



THE ACTION" OF COMPOUXBS COXTAIXING THE PYRIDIN XUCLEUS 



Pyridin forms the nucleus upon which are built many of the alka- 

 loids. It is obtained chiefly froni coal tar, but may also be obtained 

 from a number of alkaloids (trigoneUin, spartcin, cinchonin) when 

 these are highly heated, treated with alkalies, or distiUed ^nth zinc dust. 



It has been obser.'ed by Ru-KEXBUXG ('91) that the vapor of 

 pyridin and some of its homologues is poisonous to bacteria.^ The 

 action of p\Tidin and its homologues has received additional impor- 

 tance as a result of the investigations of Shorey (:o6), who obtamed 

 pmdin bv the dry distiHation of soH. The author cited sa}-s (p- 37) • 

 *^As the fat in this soH was found to be only 0.005 per cent, it does 

 not seem likelv that the p^xidin formed was due to the formation of 



