DRY-ROT OF IWCENSE CEDAR. 15 



immediately surrounding it hyphse 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, hyphse 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 hyphse 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 hyphse 

 usually extend directly from hole to hole." In some cases no hyphse 

 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. Hyphse 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 hyphse. In 

 the case of the last (highest) pocket in a diseased tree the hyphse 

 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 hyphse 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 hyphse 

 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 wood on the 

 fungus. Or it may be that the answer to the question lies in another 

 direction; that is, the hyphse in their work of destruction after a 



