OBSBEVATIONS ON CANADIAN CONIPER.E. 21 



wood might be expected to exhibit under similar conditions of treatment. As the furnace 

 fires were lighted shortly after this, the pronounced dryness of the air soon made a sensible 

 alteration in the appearance of the wood, which soon after exhibited increased fractures and 

 a widening of those already established. These changes were completed in about a month 

 however, after which there was no farther alteration beyond a continuous shrinkage in 

 volume, which was continued at a diminishing rate to the present time, a period in all of 

 about twenty months. Exudation of resin was noted in the sap wood, but this was not 

 excessive. Under the hatchet or chisel the wood was found to split with great facility, but 

 in the splitting the tendency was not to follow the direction of tlie instrument, but with 

 each Itlow of the mallet the line of fracture was quickly established in independent directions. 

 Thus separation along the line of the growth-rings was most pronounced, and in conse- 

 quence it was found difficult to secure a perfect radial fracture. It furthermore appeared 

 that the fracture was established radially along the medullary rays, and tangentially by 

 separation of the dense summer wood from the very thin walled spring wood along its outer 

 face, there being an actual rupture of the cell walls (fig. in) ; while these two lines of frac- 

 ture were again connected tangentially and radially by rupture of the dense summer wood 

 between the rows of thick-walled tracheids, and therefore along the line of the primary cell 

 wall. This seemed to indicate that under certain conditions of desiccation and mechanical 

 stress this wood might break up in a manner similar tp that described by our informant. 



The section which was allowed to dry in a warm room for a full month after removal 

 from the log exhibited no essential change ; but as under similar conditions, and during 

 the same period, the fractures in the log increased both in size and number in a conspicuous 

 degree, it became clear that seasoning in the log was an essential condition to the develop- 

 ment of such fractures. 



Section a, submitted to maceration, showed a copious growth of fungus, the mycelia of 

 which penetrated the structure freel}\ After one month of such treatment, no special alter- 

 ation was noted. Submitted to desiccation in a very dry room for three and one-half 

 months, there was no indication of an increased tendency to fracture. 



Section b, also submitted to maceration for a period of four and one-half months, was 

 also freely penetrated by the mycelia of a copious fungoid growth. After prolonged 

 desiccation in dry air, it presented precisely the same appearance as section a after its course 

 of treatment. These results seem to indicate pretty clearly that alternate maceration and 

 desiccation have no special influence in promoting a rapid breaking up of the wood in the 

 manner to which our attention was first directed, and we are, therefore, compelled to turn 

 to an examination of the structure itself for a possible explanation. 



The specimen under consideration is of that variety of Douglas fir known as the " red " 

 or " coarse-grained " variety, the one of least economic value. The growth-rings are rather 

 uniformly 1-5 mm. thick and sharply defined ; the summer wood is prominent, resinous and 

 flinty, and about one-half the spring wood or one-third the full thickness of the growth- 

 ring. (Fig. 1, plate I.) In these respects the wood presents no exceptional features (com- 

 pare figs. 2 and 3, plate I., and figs. 1-6, plate II.), as the species normally exhibits wide 

 variations in the thickness of the growth-ring, as well as in the relative volume and char- 

 acter of the summer wood. 



The resin-passages are distributed in rows, but such rows are found to occur only 

 occasionally. The i-esin-passages are found to average twenty-eight per square centimetre, 



