DHY-ROT OF INCENSE CEDAE. 15 
immediately surrounding it hyphae were found abundantly. They 
bore through, the cell walls in all directions, showing no preference 
for the bordered pits and apparently making no distinction between 
spring and summer wood. They were rarely found in the medullary 
rays. 
Harkness (7) states that "the mycelium does not leave behind the 
slightest microscopical trace of its presence in the sound wood when 
passing from pocket to pocket." In some of the brownish and straw- 
colored streaks of wood which extended vertically from pocket to 
pocket of immature decay, hyphae were found sparingly. These 
usually followed the lumen of a tracheid, but sometimes passed through 
the wall into the lumen of the adjacent tracheid. The writer was 
unable to follow the entire course of the hyphae in any case from 
pocket to pocket and therefore could not verify Von Schrenk's 
statement (26, p. 73) that " between the rotted areas the hyphae 
usually extend directly from hole to hole." In some cases no hyphae 
were encountered in the discolored streaks between the young pockets, 
but this was probably due to the failure to make sections at the proper 
place. Hyphae were commonly present in the apparently sound 
wood surrounding young pockets to a distance of 4 mm. (0.157 inch), 
and sparingly from that point to 8 mm. (0.314 inch) in a horizontal 
direction. Owing to lack of proper material it was possible to make 
only a limited study of the vertical distribution of the hyphae. In 
the case of the last (highest) pocket in a diseased tree the hyphae 
were abundant to a distance of 1.5 cm. (0.6 inch) above the pocket, 
and sparingly from that point on to 7.8 cm. (3.07 inch), where they 
ended. 
Observation leads to the inference that the hyphae are able to 
pass for some distance through the sound wood without causing the 
slightest microscopical change in the color or structure other than 
an occasional hole in a cell wall as the hypha passes from the lumen 
of one tracheid to that of another. In certain cases isolated pockets 
of decay have been found at a maximum distance of approximately 
4.3 meters (14.3 feet) from the nearest pocket of decay, yet a very 
careful analysis showed that there was only one possible means of 
entrance for the fungus into the tree, and consequently the hyphte 
must have traversed this distance through the sound wood before 
causing another pocket of decay. 
As to why the fungus decays only the wood in localized pockets 
which are separated by areas of practically sound wood it is im- 
possible to state, since nothing is known of the influence of a possible 
variation of the chemical and physical properties of the w T ood on the 
fungus. Or it may be that the answer to the question lies in another 
direction; that is, the hyphae in their work of destruction after a 
