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 high 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.u^-ety Lines for Spraying. 

 AB, clear weather; CD, cloudy weather. 



Hutn.dUjj. 



Pure acid lead arsenate 

 paste. 



Fig. 19. — Commercial acid lead 

 arsenate paste. 



Humidity 



i 



^7S 



Fig. 20. — Commercial acid lead 

 arsenate powder. 



Fig. 21. — Pure neutral lead arsenate 

 paste. 



