10 



II 



13 



li 



H 



IS 

 i6 



17 



Bcliiiri 



cm ' CO 



icih) 



Alloxan 



co<;^ j>co 



Guanin 



NHa'C'NU.CO •C'NU 



N- 



N H' 



I 



GuariuUii 



Pyridin 

 C.,Fl5N 



Picolin 



C.IUN ■ CH3 

 I'ipcruUn 





i 



C N 



CII 



Xanthin 



( O-NII-CO -C-NII 



■C N 





CH 



9 



TO 



12 



10 



7 



7 



1000 ppin 



* t * T 



100 ppra 



100 ppm 



I pptTl 



1000 ])pm 



250 ppm 



50 ppm 



500 ppiu 



25 ppm 



100 ppm 



No injury. 



Insoluble above 40 

 hannful cfFccts at 



centration. 



ppm, 

 that 



No 

 con- 



Insoluhle above 25 ppm. No 

 injurious effects at that concen- 

 tration. 



In solutions of 50 ppm and less, 

 the root growth was normal. 



a 



to 



I 



O 



o 

 CI 



3 



ri-*^TKPlW ll T 'J* ™ !! p i 



^f\* 



*^4-- 





