8 CIRCULAR 6 5 6, U. S. DEPARTMENT OF AGRICULTURE 



experiments were run with the following dressings: No. 541 with 1 per- 

 cent red oxide of copper; No. 541 with 1 percent black oxide of copper; 

 a heavy proprietary wax resembling grafting wax; a wax emulsion 

 with water; and also No. 540 and No. 541 with several different 

 thinners. After the first year, experiments with only the first six 

 preparations listed were continued, as these seemed to be the most 

 satisfactory. 



The detailed experiments reported were run from 1936 to 1938, 

 inclusive, at Arlington Experiment Farm, Arlington, Va. At about 

 the middle of each month for 2 years, circular side wounds about 25 

 millimeters in diameter were made with a 1-inch bit on the internodes 

 of limbs. One or more wounds on at least five trees were immediately 

 painted with each of the six dressings listed. In November of each 

 year, after the leaves had been killed by frost, the transverse and 

 longitudinal diameters of the wounds were measured. The wounds 

 made from October 1936 to September 1937 were measured in October 

 or November 1937 and in October or November 1938 and those made 

 from October 1937 to September 1938 in October or November 1938 

 and in October or November 1939; hence, the October wounds were 

 approximately 13 months old and the September wounds approxi- 

 mately 2 months old at the time of the measurements summarized in 

 figure 1 . Measurements summarized in figure 2 were made 1 year later 

 when the same wounds ranged from approximately 25 to 14 months in 

 age. They represent summation of healing and of dying of tissues 

 around the wounds during the part of the first season after the time of 

 wounding and through the entire second growing season. 



Because certain limbs became devitalized or, in a few cases, labels 

 were lost, it was not always possible to include in the second year's 

 data all the wounds that were in the first. Some of the irregularities 

 in the graphs for the second year may be thus explained. 



Relation of Time of Wounding and Treatment to 



Healing 



The results obtained when wounds and treatments were made at 

 monthly intervals beginning in October of one year and measured 

 the following October or November are shown graphically in figure 1 ; 

 measurements made 1 year later are shown in figure 2. As may be 

 seen by examining these figures, the longitudinal diameters of the 

 wounds almost invariably increased, the extent of elongation probably 

 serving as the best criterion for evaluating the various treatments. 

 The data in figure 1 show considerable variability, but, in general, 

 there was a tendency for greater elongation to occur in wounds made 

 in winter than in spring. 



The data of figures 1 and 2 regrouped so that those for November, 

 December, and January are averaged as one unit and those for 

 February, March, and April as another unit are graphed in figure 3. 

 Such a grouping facilitates the comparison between winter and 

 spring treatments. Although this particular grouping of months 

 does not correspond to the calendar winter and spring seasons, it 

 seems to conform more closely to the plant's response to season. 

 Figure 3, A, representing the results at the end of the first year, shows 

 that the longitudinal diameter is greater for the winter than the 

 spring wounding and treating in every case. The same general 



