466 Journal of Agricultural Research vol. i, NO. 6 



A good absorption was obtained in both the sapwood and heartwood. 

 Nevertheless, the tyloses, which were everywhere well developed and un- 

 damaged in the large vessels of both regions, remained colorless and 

 untreated. In addition, two other blocks of hickory from material col- 

 lected with special care were also given pressure treatments in the cylin- 

 der. These specimens were from pignut hickory, Hicoria glabra, and 

 mockernut hickory, Hicoria alba. Both specimens contained sapwood 

 and heartwood, with tyloses strongly developed in the large vessels. 

 Again, the wood was thoroughly treated with creosote in both the sap- 

 wood and the heartwood, and once more the tyloses could be observed 

 on a split surface to be quite uncolored and visible even to the naked 

 eye through their marked contrast with the blackish brown of the treated 

 wood. (PI. LII, fig. i.) 



Thus, results from four specimens of hickory from different sources 

 clearly showed that in spite of the presence of tyloses a high absorption 

 of creosote may be obtained in the wood substance outside of the vessels 

 and the tyloses filling them. 



The other species used in these experiments was the so-called red-heart 

 beech, a form of Fagus atropunicea. This had white tylose-free sapwood, 

 but a reddish heartwood with many tyloses. It was treated in the cylin- 

 der at the same time as some of the hickories. The sapwood was thor- 

 oughly penetrated, but the heartwood remained untreated except for a 

 surface coating and a very slight infiltration near the ends. 



Lastly, a second piece of white oak was treated, as a check on the 

 piece treated previously. After the creosote treatment, which was 

 given at the same time as that of the hickories and beech, the sapwood 

 was found to be penetrated, and, as before, the heartwood was unpene- 

 trated. Careful examination showed, however, that the discoloration 

 of the creosote extended down the large vessels of the sapwood and into 

 the tyloses which they contained. This apparent contradiction of 

 previous observations was explained when the material was examined 

 under the microscope. The tyloses were found to be full of fungous 

 mycelium and riddled with holes produced by the hyphae in passing 

 through the tylose walls. Under these circumstances, even when abun- 

 dant tyloses are present, it is clear that some penetration may be secured 

 in the vessels. 



The marked difference to be observed in the penetrance of creosote in 

 treatments of red oak and white oak is, however, chiefly the result of the 

 presence or absence of tyloses. The unobstructed vessels of red oak 

 give such open channels and offer so much additional surface for absorp- 

 tion through their walls that the penetrability of the other elements 

 lying between the vessels is of relatively little importance. In white 

 oak, on the other hand, it is only the elements of structure other than 

 the large vessels that are available for penetration. The type of pene- 

 trance obtained in red oak is shown in Plate LIX, figure 2, A. The dark 

 streaks mark the course of the creosote, which passed almost entirely 



