AEIZONA EXPEKIMENTS OX WESTEEX YELLOW PINE. 13 



conclusion of the experiment also the faces on a number of trees on 

 each area were examined. Of 276 trees inspected, the faces on 116 

 showed indications of borers. These indications, consisting of small 

 deposits of finely divided wood, were generally found on the lower 

 part of the face near the apron at the junction of the inner bark and 

 sapwood. 'Whether or not the trees were infested with borers before 

 the cups were hung is not known. It was noted that practically all 

 the trees which showed signs of borers also contained holes made by 

 woodpeckers, doubtless in search of the insects. 



Of 634 faces examined on the three areas 5 were found to be dry 

 and 26 partially dry. , 



EVAPORATION FROM CUPS. 



The rate of evaporation from the cups was determined by exposing 

 cups half full of fresh gum to the action of the air and weighing them 

 at regular intervals. The samples of gum were secured by taking 

 small amounts from as many of the cups as necessary on the first or 

 second day after a fresh streak had been put on. Two samples were 

 taken from each area after each dipping. As dip is collected every 

 three or four weeks in commercial operations, the loss in weight 

 during the first four weeks is the significant figure in the evaporation 

 tests. Forty-eight evaporation samples were used. Of these, 14 

 showed no loss at all in weight for the first four weeks ; the remaining 

 34 samples showed losses ranging from 1.5 to 10.5 per cent of the orig- 

 inal weight. The average loss in weight for all the samples was 3 per 

 cent. The gum as exposed contained turpentine, rosin, water, and 

 chips. The loss by evaporation was, of course, made up of turpen- 

 tine and water. The average loss of turpentine by evaporation 

 from the cups in the Arizona experiments was therefore less than 3 

 per cent. No evaporation figures are available for southeastern 

 operations. 



SPECIAL PROBLEMS INVESTIGATED. 



Area D contained 50 selected trees 15 inches or more in diameter 

 breast high. Two cups were hung on each tree — one on the north 

 side and one on the south side. In 25 of the trees the first streak was 

 put on so as to bring the peak of the face 3 inches above the apron. 

 In the remaining 25 trees the first streak was put on so as to bring the 

 peak 18 inches above the apron. Of the 50 selected trees about half 

 were black jack and half yellow pine. The 3-inch and 18-inch faces 

 were placed on black jack and yellow pines in about equal proportions. 

 The rough outer bark between the peak and the apron was smoothed 

 off in all of the trees. The trees were chipped every week in the 

 ordinary maimer. The cups were dipped every week and weighed 

 on the tliird^ fiith, and seventh day after each cliipping throughout 

 the season by means of a small portable balance. The dip from the 



