BORDERED PITS IN DOUGLAS FIR: A STUDY OF THE 



POSITION OF THE TORUS IN MOUNTAIN AND 



LOWLAND SPECIMENS IN RELATION 



TO CREOSOTE PENETRATION 



By Gertrude J. Griffin 

 Assistant Xylotomist, Forest Products Laboratory 



In commercial practice Douglas fir is regarded as a difficult conifer 

 in which to obtain good creosote penetration. 



Earlier investigations, conducted at the Forest Products Laboratory 

 of the Forest Service, Madison, Wisconsin, and elsewhere, indicated 

 that the bordered pits are of considerable significance in relation to 

 penetrance in conifers. 



The purpose of this study was to secure definite information as to 

 the position of the tori of the bordered pits in Douglas fir, as found 

 under a variety of conditions, and to determine, if possible, the efifect 

 of these on penetration with creosote. 



SPRINGWOOD. 



SUMMERWOOD. 



T = TORUS. 

 Fig. I. — Doi:glas fir bordered pits. 



In figure i diagrams are given of two springwood bordered pits, 

 showing the relatively thin walls, the rather long overhang of the 

 borders, and the general shape of the pit cavity. The characteristic 

 thin-pit membrane, with its thickened portion (the torus "T") of the 

 springwood pit, is shown in contrast to the appearance of this structure 

 in the summerwood. In the two summerwood pits the typically thicker 

 walls, smaller cavity, and thicker, shorter torus are noticeable. In one 

 bordered pit of the springwood and one of the summerwood the torus 



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