8 BULLETIN 871, U. S. DEPARTMENT OF AGRICULTURE. 



the decays were so badly eaten out by insects as to preclude any 

 description of the rot. By reason of this, some light infections of 

 Poly {>orus amarus may have been included under secondary rots, 

 but such cases have undoubtedly been very rare. 



Of the 59 infections of second axy rots examined, only 9 resulted 

 in culls of any importance, the highest percentage of unmerchant- 

 able timber in relation to the total volume of the tree being 19.5 

 per cent. In all the remaining 50 trees the infections were negligible. 

 These figures show secondary rots to be of only trivial importance in 

 reducing the merchantable volume; hence, such decays are not 

 further considered in this paper. 



THE DRY-ROT. 



The dry-rot of incense cedar, termed by eastern workers "pecki- 

 ness" or "pin-rot," caused by the fungus Polyporus amarus Hedge, 

 was first described and figured by Harkness (7) but no cause was 

 given. Next Von Schrenk (26, 67-77, pi. 2, 4, 5) described and 

 figured the disease without stating the cause, and later (28) he 

 mentions Polyporus libocedris, but without giving a description of 

 type specimens. Hedgcock (10) first definitely assigned the cause 

 of the dry-rot to Polyporus amarus sp. nov. and described the fungus. 

 Later Meinecke (15, p. 35-37) presented a brief description of the 

 sporophore, accompanied by a photograph of a typical fully devel- 

 oped bell-shaped specimen, with the upper surface partially destroyed 

 by insects. Murrill (24, p. 25) places the fungus in the genus Fomes. 



Harkness and Moore, Mayr, and Sargent have attributed the cause 

 of the dry-rot to Daedalea vorax Hke., but Von Schrenk (26, p. 67-68) 

 has shown this to be an error. Farlow and Seymour (5, p. 169) and 

 Bryant (1, p. 15) have made the same mistake. 



The dry-rot is very widely distributed. It has been found at 

 elevations varying from 650 to 6,480 feet as far north as Oakridge, 

 Lane County, Oreg., west to the west of China Flat, Humboldt 

 County, Calif., east to Shaver, Fresno County, Calif., and south to 

 the north and east of Mentone, San Bernardino County, Calif. In 

 fact, from all indications and hearsay evidence it is quite reasonable 

 to presume that dry-rot is more or less prevalent in incense cedar 

 throughout the range of the host (30, p. 150-152). 



THE SPOROPHORE. 



Since Hedgcock's description was published, so many sporophores 

 have been collected that the original description may be supplemented 

 by the following, which is based on the examination of 25 sporophores, 

 both fresh and old : 



I'ob/porus amarus. — Pileus soft and mushy when young, then rather tough and 

 cheesy, finally becoming hard and chalky when old, ungulate, bell shaped or occa- 





