Mar. 35, 1914 Tyloses in American Woods 467 



through the open vessels. The practical effect of this is evident in the 

 results obtained in penetrance treatments. It is possible to force creo- 

 sote for long distances through red oak just as it would be possible to 

 force it through similar distances in small open pipe lines. In com- 

 parison with this, the distance the oil will pass through white oak is very 

 short, since it has to penetrate through many cell walls, and the resistance 

 of the material must be overcome by high pressures. 



Thus, although tyloses have a distinct effect, they are not the only 

 factor in the penetrance of wood. The characteristics of the other 

 elements in the annual ring must be considered. However, in the cases 

 examined, wherever the large vessels contained abundantly developed 

 tyloses or filling cells, the vessels and the tyloses, but not necessarily 

 the rest of the woody tissues, were impenetrable to creosote. 



OBSERVATIONS ON CONIFERS 



The presence of resin canals and their condition that is, whether they 

 are open or partly or entirely closed by cells considered in conjunction 

 with the general permeability of the tracheids, is a factor of practical 

 significance in the selection of wood for creosoting. (Pis. LVI and LVII.) 

 The number of the resin canals is very small in comparison with the 

 number of tracheids. However, if the canals are unobstructed, pene- 

 trance is easily obtained for considerable distances through their cavities. 

 In a wood whose tracheids are penetrated with difficulty, the creosote 

 does not spread to any great extent from the canals into the tracheids, 

 even when the former are full. Nevertheless, the presence of creosote 

 or other toxic liquid in the resin-canal regions, which are among the first 

 affected by fungous infection, is of considerable assistance in prolonging 

 the life of the wood. Many of the resin canals, especially the vertical 

 canals in both the sapwood and the heartwood of the pines, are not com- 

 pletely closed (PI. LVII, fig. i, and PI. LVIII, figs, i and 4) and can 

 for this reason be penetrated. The effect of the presence or absence 

 of tylose-like cells in the resin canals, while a minor factor, is significant 

 in connection with the treatment of poles, ties, and paving blocks. 



EFFECT OF TYLOSES ON THE WATER-HOGGING OF WOOD 



In order to test the effect of tyloses on the water-logging of wood, some 

 roughly comparable air-dry blocks of several species were placed in a tank 

 of water and the length of time required to water-log each block suffi- 

 ciently to sink it was noted. The blocks were grouped with reference to 

 their specific gravity (dry) 1 and their actual weight. The woods in which 

 tyloses were few or wholly lacking invariably sank before those contain- 

 ing abundant tyloses. Chestnut oak sank before white oak and bur oak, 

 persimmon before osage orange, flowering dogwood before hickory, yel- 

 low poplar and aspen before catalpa, and blue beech and honey locust 



1 Sargent, C. S. Report on the Forests of North America ... 613 p., maps. Washington. 1884. 

 (U. S. lioth Census Reports, v. 9].) 



