34 FUMIGATION FOE 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 readings 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 lines, will be of advantage when a tree is so irregular in form 
that one line passing over the center of the tree seems to fail to give 
the measurement with sufficient accuracy. When 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 marking tents to aid in estimating 
dosage. — The idea of marking 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 : a 
It consists in 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, 
a Bui. 152, Cal. Agr. Exp. Sta., p. 15. 
