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



Plate V. 













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Fiq. 1.— Penetrations in Jack Pine (Pinus divaricata) Heartwood. 



1, piece No. 296, treated 30 minutes; 2, piece No. 298. treated 60 minutes: 3, piece No. 297, treated 

 120 minutes. The structure surrounding the resin ducts was easily penetrated, allowing the 

 heartwood to be satisfactorily treated. Note the well-defined radial penetration which fol- 

 lowed the radial ducts toward the pith. 



Fig. 2.— Penetrations in Tamarack (Larix laricina) Heartwood. 



1, piece No. 312, treated 30 minutes; 2, piece No. 313, treated 60 minutes; 3, piece No. 311, treated 

 120 minutes. This is a good example of a species containing resin ducts that may be easily 

 impregnated, but in which the nonresin structure is almost impenetrable. Note the absence 

 of radial or tangential penetration. 



