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



small, few. widely scattered and occurred chiefly i'n the summerwood: at fre- 

 quent intervals they were partially obstructed by constrictions. 



The average oven-dry weight per cubic foot of four heart specimens was 27.5 

 pounds, and of five sap specimens 27.7 pounds. 



This species contained "fusiform rays"; that is, rays traversed by resin 

 canals, these being smaller than the longitudinal ducts. The ray ducts fre- 

 quently crossed the longitudinal ones at right angles, thereby forming junctions. 

 This offered the possibility of a deep radial penetration through the radial 

 ducts. 



The penetration, especially in the sapwood, took place much more easily in 

 the summerwood than in the springwood. Maximum penetrations took place 

 along the resin ducts, chiefly in the summerwood ; in the springwood the ducts 

 were sometimes treated while the surrounding tracheids were not. The spring- 

 wood was always treated near the point of pressure. In the heartwood both the 

 springwood and summerwood were treated, sometimes equally but usually 

 more heavily in the latter. The sapwood was easily treated, both radially and 

 longitudinally along the two sets of ducts. 



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

 in the penetrance specimens. The summerwood was much the easier to treat, 

 but the springwood was penetrated by prolonged application of pressure. In 

 some cases springwood resin ducts were found that were not penetrated, 

 whereas the adjacent summerwood was penetrated. 



In this species there was a very great difference between penetrations and 

 absorptions in the heartwood and in the sapwood. The former appeared to be 

 almost impenetrable, while the latter was easily treated. This can be ex- 

 plained partially by the larger quantity and less soluble condition of the resin 

 in the canals of the heartwood. In sapwood the radial ducts had a very great 

 influence on penetrations, and it seems probable that this would be the case in 

 the heartwood also for long-continued treatments. There is also a great differ- 

 ence between heartwood and sapwood in the penetrability of the nonresinous 

 structure. Such penetrability is directly affected by the penetrability of the 

 ducts themselves, since creosote in the latter quickly become saturated with 

 resin which must escape to the surrounding wood before penetration can 

 continue. 



In heartwood the ratio of longitudinal to radial and tangential penetrations 

 was about 10 or 12 to 1. In sapwood longitudinal penetration was about 12 

 times radial and 100 times the tangential penetrations. 



SITKA SPRUCE (PICEA SITCHEXSIS). 



The growth rings of Sitka spruce were broad with summerwood equal to or 

 exceeding the springwood. Resin cells were wholly wanting. Resin passages 

 were few, small, and had thick-walled epithelium cells ; they were well developed 

 but frequently constricted. Tyloses were sometimes present in the resin canals. 

 The canals in the fusiform rays had also thick-walled epithelium cells. The 

 resin ducts running radially and longitudinally frequently intersected each 

 other. 



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

 19.2 pounds, and of four sap specimens 18.1 pounds. 



While the heartwood of this species contained both radial and longitudinal 

 ducts, they were not sufliciently numerous to have much influence on penetra- 

 tion. When present in the springwood the ducts were usually treated, but 

 the oil did not spread to the surrounding structure. Penetration took place 

 very rapidiy in the summerwood, which treated almost as easily as the resin 



