Bui. 101, U. S. Dept of Agriculture. 



Plate VI 



Fig. 1 .—Penetrations in Alpine Fir (Abies lasiocarpa) Heartwood. 



1, piece No. 308, treated 30 minutes; 2, piece No. 307, treated 60 minutes; 3, piece No. 309, treated 

 120 minutes. This species contained no resin ducts or cells and is almost impenetrable. 



Fig. 2.— Douglas Fir (Pseudotsuga taxifolia) Treated in Penetrance Apparatus. 



The piece to the left is sapwood; that to the right is heartwood. The spots on the sapwood 

 piece are treated resin ducts outside of the range of ordinary penetration. They show that 

 the creosote must have penetrated radially and then longitudinally. Most of the spots are in 

 the summerwood. 



