24 BULLETIN 606, IT. S. DEPARTMENT OF AGRICULTURE. 
ing the absorption and penetration to some extent. The sapwood 
was very easily treated even at low pressures. 
Gum, tupelo (Xyssa, 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 (Celtis Occident alts) — heartvjood and sapwood. — 
Tyloses occurred irregularly in both heartwood and sapwood of 
hackberry. The penetration occurred mainly in the vessels and Avood 
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 (Hicoria 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 uncolored, indicating that in this wood 
these growths were practically impermeable to creosote. 
Maple, silver {Acer saccharinum) — 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. 
