BORDERED PITS IN DOUGLAS FlR 815 



is shown in a central position, equally dividing the pit cavity. In the 

 other two bordered pits the torus is pressed to one side against the 

 opening of the pit cavity, completely closing it. For convenience and 

 brevity in describing this position of the torus, the term "aspirated" is 

 here used. 



The investigation was divided into three parts : 



1. The study of the position of the tori of the bordered pits as found 

 under rather ordinary circumstances, as, for example, in green, air-dry, 

 and oven-dry wood. 



2. The study of material which had been penetrated with creosote to 

 varying extents. This work was undertaken with a view to determin- 

 ing whether the tori of the bordered pits were always in the same posi- 

 tion whenever the material failed to absorb as much oil as was expected. 



3. A series of experiments was made to determine whether the tori 

 could be displaced or held fixed in any given position by artificial treat- 

 ments of small blocks. The test specimens were subjected to air pres- 

 sure, steam and creosote treatments, and soaking in alcohol followed 

 by oven-drying, respectively. 



CONDITION OF THE TORI IN BORDERED PITS IN NATURAL WOOD OF 

 DIFFERENT MOISTURE CONTENT 



Grccii Material. — Material from two specimens of coast, or lowland- 

 grown, Douglas fir from Everett, Washington, and from seven speci- 

 mens of mountain-grown Douglas fir from San Miguel County, New 

 Mexico, was available for this study. A comparison of the heartwood 

 and sapwood portions of both of these groups of material was made. 

 A relatively small number of the springwood pits were examined. The 

 greater part of the investigation was conducted on the summerwood 

 pits, since the summerwood is the region where penetration is most 

 general. The results of the microscopic examinations are given in 

 Table i. 



It is of particular interest to note that, in the summerwood of the 

 mountain-grown specimens especially, a considerable number of the 

 tori of the bordered pits were not in the central or generally considered 

 usual position, but had been displaced or aspirated — that is, moved to 

 one side of the pit cavity. 



Air-dr\ Material. — One untreated specimen of air-dry mountain- 

 grown Douglas fir. from Missoula County, Montana, and one specimen 

 of untreated air-dry Douglas fir from a tree which had grown half wa\ 



