20 



BULLETIN" 1064, U. S. DEPARTMENT OF AGRICULTURE. 



Tables 2 and 3 results are given from a set of chips obtained at the 

 last streak cut and a set of increment borings made 2 to 3 inches to 

 the side of the face at the height of the last streak. The borings, in 

 general, showed less effect from the turpentining than the chips, indi- 

 cating that the response to the wound was not as marked tangentially 

 or circumferentially as it was vertically. The double and the stand- 

 ard both showed more reduction in wood formation than the narrow, 

 as indicated by ring width. Judged by the borings alone, the double 

 showed slightly greater reduction than the standard. The chips, on 

 the other hand, showed more reduction in ring width in the standard 

 than in the double. This tendency, however, did not hold for the 



Mar Apr. May June Ju/y Auo. 5<zpr. Oct. /Vok Mar Apr. May June Jo/y Aoy. Sapr Ccr. /Vor. 



Fig. 4. — Double trees, 1917. 



Number of tracheids, observed March to 

 November ; in 1917, growth ring. ° Sum- 

 mer wood present. 



Number of resin centers per unit area 

 (an arbitrary tangential extent ; diameter 

 of microscopic field by the width of the 

 annual ring observed). Observed March to 

 November, 1917 ; in 1915, 1916, and 1917, 

 growth rings. 



amount of summer wood present, which was exceptionally reduced 

 in the specimens from the double tract. It would appear that the 

 double chipping produced a special response which was manifest in 

 the increased ring width shown by the chip specimens and in the 

 sustained relatively high yield for the second year, which has been 

 mentioned. It would seem, however, that this response was accom- 

 polished at the expense of summerwood production and of the tree's 

 vitality in general, judging by such indications as these and by the 

 frequent occurrence of " dry " faces in this crop. The double also 

 produced fewer resin passages than the narrow. In 1917 (Table 4) 

 the reduction in wood formation in the specimens collected from 50 



