12 



BULLETIN 60G, U. S. DEPARTMENT OF AGRICULTURE. 



average of three specimens of each species treated in the penetrance 

 apparatus, and the absorptions are the average of seven specimens 

 treated in the cylinder. However, a close relation between penetra- 

 tion and absorption could not be expected in manj^ of the species. 

 For example, species such as red oak and chestnut oak have large 

 open pores or vessels which allow the preservative to pass easily 

 from one end of the stick to the other. The wood prosenchyma of 

 these species is very difficult to penetrate and treatment results 

 mainly in coating the vessel walls with the preservative and not in 



AVERA<3E ASSfiRPTlOH 

 , L03.PERCU. FT. 



KEC (SUK__ 



KiIITE OAK_ 



RED HEART SEECH__ 



BUR OAK 



ROCK ELM 



CHESTNUT 



SVCAMORE 



HACKBERRY 



HICKORY 



SUGAR MAPLE 



SAGK3EHRY. 

 CHESTNUT OAK 

 RED OAK 



KKITE HEART BEECH 

 YELLOKf BIRCH 



RED 



BLACK WILLOW 

 LARGE TOOTH ASPEM- 



WlliTE ELK 



GHEES* ASH 



SLIPPERY ELR3 

 SILVER MAPLE. 

 SWEET S!BCH_ 



REE- GUHS 



YSKITE ASH 



SILVER MAPLE 



EASSWOOP 



TUPELO GUfS 

 CTLDREUCHERRV- 

 TUPELO CUM 



Fig. 3. — Comparative absorptions and penetrations. 



a complete impregnation of the wood substance. Slippery elm has 

 large open vessels similar to those of red oak and chestnut oak, but 

 in this case the wood prosenchyma readily absorbs the preservative. 

 It was therefore possible to secure both a complete penetration and a 

 fairly heavy absorption in this wood. In hickory, the large vessels 

 are almost completely closed by tyloses, but a fairly good penetration 

 was obtained on account of the comparative ease with which the wood 

 prosenchyma absorbed creosote. Species in which the tyloses are 

 more or less irregularly distributed, such as black willow and large- 



