DRY-ROT OF INCENSE CEDAE. 17 



decay collected on incense cedar in Oregon. As far as the writer can 

 ascertain, this is the only collection of its kind now known. Neither 

 of these two decays affects the living sapwood. 



The mycelium of both is the same and differs from the mycelium 

 of typical dry-rot. Studies were made where these two decays were 

 distinct, where they graded into one another, and where they graded 

 into the typical dry-rot. The hyphas vary from hyaline to dark 

 brown in color, with a diameter ranging from 0.8 to 6.7 n but most 

 commonly 3 /jl. The heavier brown hyphas often branch profusely, 

 the branches becoming smaller and lighter in color. The smallest 

 ones are usually hyaline, and so are some of the larger hyphas. In 

 some instances the smaller hyphas are merely continuations of the 

 heavier strands. The hyphas are sparsely septate, often constricted 

 at the septa and without clamp connections. They bore through the 

 cell walls in all directions, but seemingly more often through the 

 tangential walls. No preference is shown for the bordered pits. They 

 are characteristically. sharply constricted when passing through the 

 walls of the tracheids and have marked attachment organs. The 

 hyphas did not enlarge in the secondary lamellae when boring through 

 the wall, as is shown by Hartig (8, 9) for Trametes pini. Quite typi- 

 cally, a single strand may pass tangentially through as many as 20 

 or 30 tracheids, often completely traversing an annual ring, without 

 sending any side branches into the lumens. This mycelium appears 

 to agree closely with that described and figured by Von Schrenk 

 (26, pp. 73-74, pis. 4-5), but which he assumed to be secondary and 

 in no way connected with the dry-rot. Often the hyphas seem to 

 pierce a cell wall without developing in the lumen of the tracheid 

 entered, a condition recorded by Hartig (8, p. 46) for Trametes pini. 

 However, in so many cases unattached fragments of hyphse were 

 found in tracheids through the walls of which the hyphas had pene- 

 trated without developing in the lumen that most probably the hyphss 

 did develop but were broken off in sectioning. 



In all, 80 trees which contained one or both of these decays were 

 dissected. The Trametes pini decay occurred alone in 61 of these, 

 the dry-rot in small pockets in 11, and both forms in 8 trees. In 28 

 of the 61 trees having the Trametes pini decay, this was either inter- 

 mingled, graded into, or very close to pockets of typical decay without 

 there being any line of demarcation between the two. In certain 

 cases the two decays could be absolutely traced to the same source of 

 infection. Tree No. 40 on the intermediate area forms an excellent 

 example. This tree had two small open fire scars in the butt just at 

 ground level. There was a light infection of typical pockets of dry-rot 

 extending from ground level to a height of 7.3 feet. At this point 

 Trametes pini decay appeared without any line of demarcation and 

 182803°— 20— Bull. 871—3 



