DRY-ROT OF INCENSE CEDAR. 



sionally subapplanate, often spuriously stipitate from knot holes, 4 to 15 by 5 to 22 

 by 5 to 20 cm., commonly 7 to 10 by 11 to 13 by 8 to 13 cm., occasionally abortive 

 without hymenial layer, then assuming irregular shapes; surface pubescent when young, 

 rimose and chalky when old, at first buff, then tan, and often blotched with brown 

 when attacked by insects; margin obtuse, frequently having an outer band of darker 

 brown, often slightly furrowed; context homogeneous, 1 lemon-yellow, later buff to 

 tan, usually darker near the surface when old, slightly bitter to the taste, 4 to 14 cm. 

 thick, commonly 9 to 11 cm., usually friable when dry but occasionally becoming 

 partially horny, hard; tubes not stratified, lemon-yellow within, cylindric 0.2 to 3 

 cm. in length, shorter next the margin, mouths circular or slightly irregular, 1 to 3 

 to a millimeter, lemon or sulphur yellow during growth, turning brown when bruised 

 or old, becoming lacerate; under surface of the hymenial layer sometimes exuding 

 clear yellow drops of liquid, sweetish to taste; spores hyaline or slightly tinged with 

 yellowish brown, smooth, ovoid (200) range 3 to 6.5 n by 4.5 to 9 n; standard size 

 3.5 to 4.5 n by 6.5 to 7 ju, nucleated; cystidia none. 



The following table presents detailed measurements of 24 sporo- 

 phores of Polyporus amarus: 



Table I. — Sporophore measurements of the incense-cedar dry-rot fungus. 



cm. cm. cm. 



cm. cm. cm. 



cm. cm. cm. 



3. 8 by 4. 8 by 8.3 



8. by 13. by 13. 



9. 5 by 17.0 by 13. 3 



4. 2 by 5. 5 by 5.5 



9.0 by 11. 5 by 9.9 



9. 8 by 13. 2 by 13.0 



6.0 by 7. 3 by 8.6 



9.0 by 10.0 by 10.0 



10. 3 by 14. 9 by 14. 8 



6. 8 by 11. 2 by 12.3 



9.0 by 10. 5 by 11.0 



11. 4 by 20. 7 by 19. 8 



7. 5 by 11. 4 by 9.0 



9.0 by 13. 3 by 12.0 



12.0 by 16. 4 by 10. 8 



7. 5 by 17.0 by 8.1 



9.1 by 10. 7 by 8.5 



12. 1 by 21. 2 by 12.5 



7. 6 by 11. 4 by 9.5 



9.1 by 12. 4 by 8.9 



14. 5 by 22.0 by 13. 



8. by 12. 5 by 10. 



9. 5 by 14. 7 by 11.0 



14. 8 by 12. 7 by 16. 5 



The sporophores, which last for one season only even at best, are 

 not at all common, a statement which is supported by the number 

 of years the dry-rot was known before the cause was definitely 

 determined. During certain years sporophores seem to be very 

 rare. They most commonly occur in the summer, and especially 

 in the fall, but occasionally are found at other seasons. Observa- 

 tions record two fresh ones in March in a rather mild climate at an 

 altitude of about 3,000 feet in the Sierra Nevada. Another was 

 found in a different locality in June. No sporophores have been 

 found developing later than October, but occasional fresh ones 

 may be carried over from a previous fall into the winter in a frozen 

 condition. They are then destroyed in the spring. 



Typically the sporophores are produced on living trees but are, 

 on occasions, found on dead fallen trees. (PL I.) Seven such cases 

 have been observed during the past five years. In five of these it 

 was possible to determine the time which elapsed between the felling 

 of the tree and the appearance of the sporophore. Three of the 

 sporophores were produced 3 years, one 4 years, and one 27 years 

 after the trees had been cut. As to how long the mycelium may 



1 The substance of the sporophore not including the outer layers. 

 182803°— 20— Bull. 871 2 



