SHADE TREES. 



183 



field, Mass., who has made quite a httle use of ehistic cement for cavity 

 work. One of the drawbacks in the use of this substance for tree work 

 is that it does not harden suffi- 

 ciently, the surface easily becoming- 

 disfigured. On the other hand, it 

 is valual)le for cavities in high 

 swaying trunks and limbs of trees, 

 and especially for cavities witli 

 horizontal openings. 



Wood pulp with a thin facing of 

 Portland cement has also been em- 

 ployed for covering the openings 

 of cavities. 



Asphalt Fillings. — During the 

 last twenty years numerous at- 

 tempts have been made to use 

 asphalt in tree repair work, and 

 more recently it has been employed 

 in combination with other sub- 

 stances. Asphalt and sawdust 

 have been used for cavity work by 

 Mr. John Boddy,^ city forester of 

 Cleveland, Ohio. For cavities in 

 swaying branches he uses 1 part 



Fi<i. 53. — Cavity in apple tree cleaned out, 

 treated antiseptically, and surface covered 

 with tin. 



Fig. 54. — Elastic cement covering of cavity 

 opening. Wire mesh only supports the thin 

 covering of cement. (After L. F. Prouty.) 



asphalt to 3 or 4 parts sawdust, 

 and for other cavities 1 part 

 asphalt to 5 or 6 parts sawdust. 

 The sawdust is stirred into the hot 

 asphaltum until the desired con- 

 sistency is obtained, and the 

 mixture while still hot is put 

 into the cavities with tools 

 smeared with crude oil. Mr. 

 Boddy recommends a grade of 

 asphaltum termed "Byerlyte" as 

 best suited for this purpose. This 

 is derived from refining petroleum 

 with an asphaltum basis, and is 

 the same as that used on street 

 pavements. The mixture of 

 asphaltum and sawdust is better 

 adapted physically to the move- 

 ments of the trees than the more 

 rigid Portland cement. 



1 Ohio Agr. 

 .June 11, 1915. 



Exp. Sta. Cir. No. 150, 



