MEASURING TREES. 31 



by any citrus grower contemplating the use of fumigation for the 

 white fly. This has been thoroughly demonstrated by the experi- 

 mental work conducted in the winter of 1907-8, when, as has been 

 stated, approximately 4,000 trees were fumigated. 



Methods followed in ex'perimental work. — The measurements of 

 tented trees in the experiments conducted in January and February, 

 1907, were made by means of a tape measure attached to a reel. In 

 obtaining the distance over in each case the end of the tape was held 

 in one hand while the reel was thrown over the center of the tent and 

 the measurement made from ground to ground. For the purposes of 

 the experiments, accuracy being desired as far as possible, measure- 

 ments were made in two directions, from east to west and from north to 

 south. In each case care was used to have the tape pass as nearly as 

 possible over the center of the tree regardless of the highest point. Of 

 72 tented trees measured in two directions, 70 per cent were found to' 

 vary 12 inches or less in the two measurements, 15 per cent to vary 

 from 1.3 inches to 24 inches, and 1 1 per cent from 25 inches to 50 inches. 

 The average variation was 12 inches and the maximum 50 inches. 

 Inasmuch as it is recommended that in using the table appended 

 hereto the number in the first column next above the actual measure- 

 ment (when the actual measurement is more than 6 inches above an 

 even number) be selected in estimating the dosage, it is evident that in 

 nearly all cases a measurement over the top of the tented tree in one 

 direction, together wdth the circumference, will show the dosage with 

 sufficient accuracy for practical purposes. A fumigator should, how- 

 ever, in using the table and knowing the measurement over in one 

 direction, make allowances in case the irregular shape of the tree 

 makes the single measurement over the top fall short of indicating the 

 true size. 



A new scheme for obtaining measurements. — The measuring of the 

 tented tree by means of the tape, as described, requires two men, 

 owing to the difficulty of getting the tape over the center of the 

 tree. Ordinarily it requires only one or two minutes at the most to 

 obtain these measurements, but when more than a few trees are to be 

 treated a simpler and quicker process is necessary. One man can 

 quickly obtain the circumference by using a tape provided at the end 

 wath means for attaching to the tent, wliile he walks once around the 

 tree to the starting point, unreeHng the tape as needed. For attach- 

 ing the tape to the tent some form of metal clamp, such as is usually 

 found in stock at gentlemen's furnishing stores, is suggested. In 

 fumigating on a large scale the use of a tape causes considerable 

 trouble, owing to unavoidable tangHng and misplacing, especially 

 when used at night. One of the operators, however, should always 

 estimate the circumference of the tented tree by pacing. This can not 

 be done with suflficient accuracy without considerable preHminary 

 49918— Bull. 76—08 3 



