26 BULLETIN 101, U. S. DEPARTMENT OF AGRICULTURE. 



some growth rings the springwood was treated to the center, but never as 

 heavily as the summerwood. The treatment was, as a rule, not at all uniform, 

 and considerable resistance was offered to penetration. While sapwood was 

 more penetrable than heartwood, it was, nevertheless, very difficult to treat. 

 The longitudinal penetration was from 35 to 40 times greater than the radial 

 or tangential penetrations. 



EKGELMASK SPRUCE (PICEA ENGELMANNl). 



In Engelmann spruce the growth rings were broad; the surnnierwood was 

 open, and one-third to one-half the width of the springwood. Resin cells are 

 never present. The resin passages were large but few, and did not contain 

 tyloses. The fusiform rays contained large radial ducts surrounded by thick- 

 walled epithelial cells. 



The average oven-dry weight per cubic foot of six heart specimens was 24.7 

 pounds, and of five sap specimens 25.9 pounds. 



In the heartwood the penetration was chiefly in the summerwood, but a few 

 springwood tracheids were treated near the point of pressure. Resin ducts 

 seemed to be treated with difficulty and did not appear to assist greatly in the 

 penetration. The rays were frequently treated, whether containing resin canals 

 or not. The penetration of the rays most frequently extended over from one 

 to three growth rings and seemed to start from summerwood bands. 



Penetration in the sapwood . seemed to be chiefly in the resin ducts. The 

 summerwood bands and medullary rays were also treated, but penetration 

 here took place much more slowly than through the resin ducts. Complete 

 longitudinal and radial penetration occurred through the ducts only. 



The cylinder tests showed that in heartwood the summerwood bands were all 

 treated to the center of the stick. Resin ducts were sometimes treated, some- 

 times not. Most of the medullary rays were penetrated. In the sapwood the 

 summerwood was treated as in the heartwood, and in places the springwood was 

 equally well treated. Usually, however, the springwood was only partially 

 treated, as was indicated by its golden-brown color; the treated summerwood 

 was nearly black. 



Radial penetration in this species seemed to be due largely to the rays. Ap- 

 parently, creosote passed from the summerwood to the rays and thence to 

 the next summerwood band, leaving the intervening springwood untreated. 

 Resin ducts were very important factors in the sapwood penetration, but not 

 in the heartwood. The sapwood treated almost instantly and absorbed more 

 oil than the heartwood which was very difficult to penetrate. This difference 

 was one existing chiefly in the springwood of the heart and of the sap respec- 

 tively. In the latter the springwood was, as a rule, very heavily treated, but 

 not so in the former. 



The longitudinal penetration averaged about four times the radial in heart- 

 wood and 20 times the radial in sapwood. It was about 50 times the tan- 

 gential penetrations in both heart and sap. 



WESTERN LARCH (LARIX OCCIDENTALIS) . 



In the western larch specimens the summerwood was equal to about one-half 

 the width of the springwood. The spring tracheids were large and very thin- 

 walled. Resin cells were scattered on the outer face of the surmnerwood. 

 Resin passages were large, not numerous, without tyloses, and surrounded by 

 thick-walled epithelial cells. The radial canals were large and not very 

 numerous. 



