FUMIGATION OF CITRUS PLANTS. 



11 



ment. That this environment may modify the degree of plant injury 

 is shown in the following experiments, which indicate the influence 

 of different light intensities and of different temperatures on citrus 

 plants immediately after fumigation with hydrocyanic acid. These 

 experiments were performed, some in darkness and some in the shade, 

 at temperatures ranging from 60° to 91 ° F. All plants in each experi- 

 ment were fumigated at the same time, part being placed immediately 

 after treatment in direct sunshine, part in the shade, and, excepting 

 Nos. 11, 13, and 19, part in darkness. An effort was made in several 

 experiments to have the shade temperature approximate that of 

 the sunshine, thereby eliminating consideration of the heat factor and 

 furnishing an exact basis for determining the influence of the sun's 

 direct rays, a factor of special consideration. Most of the experiments 

 also contain postfumigation environments of shade or darkness at 

 decidedly cooler temperatures than those of sunshine, and thus 

 furnish data for study of comparative temperature influences. Four 

 experiments, Nos. 12, 14, 15, and 18, include plants under three 

 different prefumigation environments, each set of which was sub- 

 jected to either four or five different postfumigation conditions. 

 Such experiments offer a wide range of data on the influence of 

 various prefumigation as well as postfumigation factors. 



EXPERIMENT 10. 



Condition during fumigation, dark, 64° F. 

 Condition before fumigation, dark, 64° F. 

 Dosage, 1 ounce NaCN. 

 Date, September 22, 1915, 7-7.40 a. m. 

 Plants in each test, 4; total, 20. 



Results. 



Condition after fumigation. 



Dark, 65° F.i 



Shade, 65° F.i 



Dark, 79° F.2 



Shade, 79° F.2 



Sun, 79° F.2 



2 



2 



2 



2 



4 



1 At cool temperatures throughout the day. 



2 At equal temperatures throughout the day. Maximum 102° F. at 2 p. m. 



EXPERIMENT 11. 



Condition during fumigation, dark, 61° F. 



Condition before fumigation, shade, 61° F. 



Dosage, 1 ounce KCN. 



Date, June 17, 1914, 8.15-9 a. m. 



Plants in each test, 3; total, 12. 



Remarks: Condition of plants comparatively tender. All at equal temperatures 

 throughout the day after fumigation. Maximum 83° F. at 2 p. m. Plants wet imme- 

 diately before fumigation. 



