1915] 



BURT THELEPHORACEAE OP NORTH AMERICA. V 765 



reflexed, hence the species must be included in Sebacina, The 

 distinguishing specific characters are easy separation as an 

 unbroken membrane of the moist fructification from the sub- 

 stratum, thickness of fructification, and position of the basidia 

 at the surface of the hymenium. 



Specimens examined: 

 Idaho: Kaniksu National Forest, Priest River, J. R. Weir, 



13. S. plumbea Burt, n. sp. Plate 27, fig. 20. 

 Type: in Burt Herb. 



Fructification effused, closely adnate, drying blackish 



plumbeous, pruinose, the margin indeterminate; structure in 



section, 150-200 /x thick, with (1) a broad layer 



next to the substratum containing much 



crystalline matter in the interspaces between 



the interwoven suberect hyphae l|-2 n in 



diameter, the wall gelatinously modified, and 



(2) a hymenial layer about 60 n thick consist- 



s i^^mbe '^^^ ^^ basidia, and of hyphae which branch and 



Basidia and form a densely interwoven hymenial surface ; 



yp aex . basidia about 30 n below the surface of 



hymenium, longitudinally septate, pyrif orm, 15-18 X 10-13 /z ; 



spores colorless, simple, even, curved, 13-15 X 4|-6 /i. 



Fructification 4-8 cm. long, |-1 cm. broad. 



On blackened wood of Populus trichocarpa. Washington. 



November. 



The coloration and habit of specimens of this species agree 

 closely with those of the European Corticium plumb eum Fr. 

 which have been received from Karsten, but the internal struc- 

 ture is wholly different from that of the latter. 



Specimens examined : 

 Washington : Bingen, W. N. Suksdorf, 863, type. 



14. S. atrata Burt, n. sp. Plate 27, fig. 21. 

 Type : in Burt Herb, and in Farlow Herb. 

 Fructification effused, somewhat gelatinous, closely adnate, 



grayish when moist, drying dark mouse-gray and shining, the 

 margin thinning out and indeterminate; structure in section. 



