34 FUMIGATION FOR THE CITRUS WHITE FLY. 



possible to estimate, the readings will differ by 2 or 3 feet, often 

 more. As the tent should always be pulled lengthwise of the strips, 

 the central line will most often lie over the center of the tree, and 

 hence be most useful in obtaining the distance over from ground 

 to ground. Frequently, however, this measurement of the tented 

 tree can be best obtained by selecting for the purpose one or the 

 other of the outside lines. The distance over the top in all cases is 

 the sum of the two readmgs on the line selected. The fourth line, 

 painted at right angles to the three running lengthwise, passing 

 through the middle point of each, extending to the sides of the tent 

 and marked with the distances corresponding to those on the first 

 three Imes, will be of advantage when a tree is so irregular m form 

 that one line passing over the center of the tree seems to fail to give 

 the measurement with sufficient accuracy. Wlien it is necessary to 

 use this line the tent can be readily pulled directly forward or back- 

 ward whatever distance is necessary to bring this line as nearly as 

 possible over the center of the tree, leaving the longitudinal line 

 (previously selected as the one passing most nearly over the center) 

 in the same relative position as before. The average of the read- 

 ings on the two lines will give the desired dimension as nearly cor- 

 rect as is necessary. Measurements of a few such irregular trees 

 will assist the operator's judgment until his experience is sufficient 

 to enable him to estimate the allowance in ordinary cases when 

 necessary. The tables appended, however, give a margin above the 

 average requirements which will cover ordinary cases of variation 

 from the regular forms. 



When a single longitudinal line is used on the smaller sized tents 

 this line can be readily brought to any desired position by pulling 

 sidewise on the tent, without the risk of damage by ripping at the 

 seams, as with the larger sizes. The lines, in addition to their use- 

 fulness in estimating the dosage, will be found of considerable assist- 

 ance in locating the catch rings, and in other ways, when handling 

 the tent. 



Previously proposed schemes for marhing tents to aid in estimating 

 dosage. — The idea of markmg the tents to aid in determining the dose 

 is not a new one, for in California several years ago a tent was in- 

 vented which was marked with concentric rings, at each of which 

 a dose was indicated. This failed to take into consideration the 

 variation in circumference of tented trees whose distance over is the 

 same. Professor Woodworth has suggested a system of marking 

 tents, concerning which he says : "• 



It consists iu making a series of parallel lines near two opposite edges of the tent, 

 which are so distanced from the center point that they shall correspond with the 

 dosage of a tree of the average shape. Upon these lines will be placed numerals, 



«Bul. 152, Cal. Agr. Exp. Sta., p. 15. 



