16 



MASS. EXPERIMENT STATION BULLETIN 207. 



General conclusions as to the plum, so far as the evidence goes, are: first, 

 that this tree is far less resistant to arsenicals under certain conditions of 

 T and H than the cherry; second, that in clear weather it is less sensitive 

 to higli humidities than to high temperatures when the other factor is low; 

 third, that this last does not hold for the acid paste and powder in cloudy 

 weather; and fourth, that again the neutral lead arsenate is the safest of 

 the materials used. 



Peach — S.vfety Lines for Spraying. 

 AB, clear weather; CD, cloudy weather. 

 Hamiditu. 



SO 



9i- 



(,0 



76- 



Humt.di.tu. 

 70 iO 



Fig. 18. 



Pure acid lead arsenate 

 paste. 



Fig. 19. — Commercial acid lead 

 arsenate paste. 



Fia. 20. — Commercial acid lead 

 arsenate powder. 



Fio. 21. — Pure neutral lead arsenate 

 paste. 



