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



ALPINE FIR (ABIES LASIOCARPA). 



The Alpine fir was very light, soft, close-grained, and compact. The growth 

 rings were narrow and uniform in width, and the summerwood was thin. The 

 springwood tracheids were large and had rather thin walls. Neither resin 

 cells nor resin canals were present. 



The average oven-dry weight per cubic foot of three sap specimens was 22 

 pounds, and of six heart specimens 22.2 pounds. 



The penetration took place more readily in the summerwood than in the 

 springwood, and in many cases only the last half dozen rows of tracheids of 

 the summerwood were treated. 



The character of penetration in the cylinder treatments was quite similar to 

 that in the penetrance tests. Although the summerwood was often treated 

 throughout the stick, in most cases only a few tracheids of the summerwood 

 were penetrated. The springwood penetration averaged about 0.15 inch longi- 

 tudinally. In some places, however, the springwood of several growth rings 

 was treated to the center of the stick. 



The sapwood apparently treated a little more easily than the heartwood, but 

 the difference was so small as to be negligible. Radial and tangential penetra- 

 tions were both of slight importance. The average longitudinal penetration 

 was 60 to 70 times as great as the average radial and tangential penetrations. 



EASTERN HEMLOCK (TSUGA CANADENSIS). 



The summerwood of eastern hemlock was dense and was from one-fourth to 

 one-half the width of the springwood. The latter had large and very thin- 

 walled tracheids. 



The average oven-dry weight per cubic foot of eight sap specimens was 20.7 

 pounds, and of eight heart specimens 22.7 pounds. 



This species is simple in structure. It differs from the yew and Alpine fir, 

 however, in having large but not numerous resin cells located in a single row on 

 the outer face of the summerwood. Resin passages are never present. 



The penetration took place more readily in the summerwood than in the 

 springwood, but near the point of pressure the springwood was penetrated in 

 some cases for 1 or 2 inches. The summerwood treated most quickly in the 

 two to five last-formed rows of summer tracheids, and apparently the heaviest 

 absorptions were along the zone of the resin cells. The line between the treated 

 summerwood and the untreated adjacent springwood was very sharply defined. 



The character of penetration in the cylinder-treated sticks was very similar 

 to that in the penetrance specimens. The summerwood was in most cases 

 treated to the center of the stick. The springwood was treated from 2 to 3 

 inches longitudinally. 



Practically no difference either in absorption or penetration was noted be- 

 tween the heartwood and sapwood. Radial and tangential penetrations were 

 of small importance. The longitudinal penetration averaged about 80 times the 

 radial or tangential penetrations. 



The influence of the resin cells on penetration was very difficult to determine. 

 The creosote appeared to penetrate more easily in the summerwood tracheids 

 lying adjacent to the resin cells, but the adjacent springwood tracheids were not 

 treated. 



A peculiarity of hemlock was its tendency to exude oil for many hours after 

 treatment. This probably was due to the slow escape of confined air in the 

 wood, which remained under a slight pressure for many hours after the release 

 of external pressure. 



