314 Report of the DEi'MtTMicxT of P]xtomol»ogy of the 



periods in which sets of trees were covered, fumigated and un- 

 covered in forty minutes. At this rate it was estimated that 

 with the same number of men and six furaigators ninety trees 

 could have been fumigated in ten hours. Possibly with a set of 

 twelve fumigators one operator with a crew of eight men might 

 have fumigated one hundred and fifty to one hundred and eighty 

 trees in ten hours, but in no case would it be possible for them 

 to fumigate two hundred trees in the same time. 



Advantages. — The principal advantages of this style of fumi- 

 gator lie in the fact that it is of constant capacity so that the 

 operator does not need to guess at size of trees and vary the 

 amount of chemicals used for each; that it can be placed around 

 a tree and not require a derrick to lift it over the same, as is the 

 case with tents and the Emory fumigator; that it contains a 

 minimum amount of waste space compared to its size, and can 

 be stored in comparatively small space. In addition it has the 

 advantage of rarely breaking the trees or rubbing off the buds. 



ESTIMATING CONTENTS OF TENTS OVER TREES. 



The method usually followed in California has been to esti- 

 mate the height of a tree and diameter through the foliage, and 

 from this the amounts of chemicals to be used are determined 

 by tables jireviously computed. Johnson^ has given a similar 

 table but there is an error in his method of estimating the cubic 

 contents of tented trees with the result that the amounts given 

 in the table are in most cases nearly double what they should 

 be, providing he intended to use but .20 gram potassium cj-anide 

 per cubic foot as stated. The amounts given in table show that 

 about .40 gram per cu. ft. was used. He gives the following 

 rule for estimating contents: " First, I calculated the contents 

 of a cylinder whose height and diameter are the height and di- 

 ameter of the tree, then calculated the contents of a sphere 

 whose diameter is the height of the tree. Then by taking half 

 the difference and adding it to the contents of the cylinder, I 



' Md. Agr. Exp. Sta. Bui. 57, p. 79. 



