24 BULLETIN 606, U. S. DEPARTMENT OF AGRICULTURE. 



ing the absorption and penetration to some extent. The sapwood 

 was very easily treated even at low pressures. 



Gum, tupelo {Nyssa, sp.) — heartwood and sapwood. — In tupelo 

 gum the pores are numerous, of medium size, and usually evenly dis- 

 tributed. No tyloses were found in the species treated. On account 

 of the numerous vessels and penetrable structure of the fiber walls, 

 good penetrations were obtained. Both the heartwood and sapwood. 

 treated very easily even at low pressure. Sapwood specimens were 

 well penetrated when immersed for an hour in the preservative with- 

 out pressure. 



Ilackberry {Celt-is occidentalis) — heartwood and sapwood. — 

 Tyloses occurred irregularly in both heartwood and sapwood of 

 hackberry. The penetration occurred mainly in the vessels and wood 

 prosenchyma and to a small extent in the medullary rays. The 

 sapwood was fairly easily penetrated even at low pressures, par- 

 ticularly in the summerwood. With the higher pressures used in 

 the cylinder treatments, both springwood and summerwood were well 

 penetrated. The heartwood showed an irregular penetration in all 

 of the cylinder treatments, due, in part, to the abundant tyloses in 

 the vessels of the untreated portions. The springwood was found 

 to be much more difficult to treat than the summerwood because 

 many well developed tyloses closed the large springwood vessels. 



Hickory, mockernut (Ilicoria alba) — heartwood. — Hickory is a 

 ring-porous wood, in which the fibers are relatively thick-walled and 

 tyloses are generally abundant in both sapwood and heartwood. All 

 the specimens showed a fairly uniform penetration, and those treated 

 in the cylinder were well penetrated when pressures of 50 pounds 

 or more were employed. Creosote was found to have penetrated 

 mainly in the wood prosenchyma, and there was little or no pene- 

 tration in the vessels or in the medullary rays. It is probable that 

 the abundance of tyloses in the vessels effectively closed them against 

 the entrance of the preservative. Penetration in this species would, 

 therefore, seem to be dependent on the ease with which the wood 

 prosenchyma can be treated. In even the most thoroughly penetrated 

 specimens the tyloses remain uneolorecl, indicating that in this wood 

 these growths were practically impermeable to creosote. 



Maple, silver {Acer saecharinum) — heartwood and sapwood. — Sil- 

 ver maple is a diffuse-porous wood. No tyloses were present in the 

 specimens treated. Both the sapwood and heartwood were found to 

 be fairly easy to treat, but more variation in penetration was found 

 in the heartwood specimens. At low pressures the heartwood showed 

 a mottled or streaked appearance, probably due to the presence of 

 gums. A good penetration was secured in the sapwood at pressures 

 over 25 pounds per square inch. Penetration took place mainly in 

 the vessels and wood prosenchyma and was very slight in the 

 medullary rays. 



