February, 1930] agricultural experiments 1929 



19 



of the trees were found to carry a larger amount of residue than those on 

 the upper branches. 



A close correlation exists between the amounts of arsenic present and 

 the quantity of lead residue, although the amount of lead recovered is 

 slightly less than would be expected in combination with the amount of 

 arsenic present. 



Slightly over 23 per cent of the apples receiving three sprays of arsenate 

 of lead, at the rate of two pounds to 50 gallons of spray, contained enough 

 arsenical residue to exceed the tolerance. Calcium arsenate used at 13/^ 

 pounds to 50 gallons of water left a residue which exceeded the tolerance 

 on 12.78 per cent of the apples. None of the apples given one spray of 

 lead arsenate contained an excess of arsenic ; calcium arsenate in excess of 

 the tolerance remained on two per cent of the apples given one spray. 

 Thirty-four per cent of the apples given three sprays, and 6.25 per cent 

 of the apples given only one cover spray, contained a residue of lead in 

 excess of the tolerance. 



The analyses were made by S. R. Shimer, G. P. Percival, and A. D. 

 Robinson under the direction of T. G. Phillips. G. F. Potter directed the 

 spraying. {Purnell Fund.) 



PREVENTING FUMIGATION INJURY IN GREENHOUSES 



The composition of the Bordeaux mixture used on greenhouse plants 

 before fumigation with cyanide is found by R. R. Jenkins and O. Butler 

 to have a marked effect on the severity of injury from fumigation. Mix- 



Figure 4. — Both of tht'se plants were sprayed with the same materials and then fumi- 

 gated. Later the one at the right was wetted, and the one at the left not. Wetting was 

 not found injurious, however, when a neutral Bordeaux mixture was used. 



