MurRILL: POLYPORACEAE OF NortTH AMERICA 425 
thought to be responsible for the common name of “ Sweet Knot,” 
by which it is known in some sections. 
The most common host of this species is the oak, especially 
Quercus nigra; but it also occurs on beech. The fruit bodies are 
found on old dead trunks. 
Exsiccatae: Rav. Fung. Car. 3: 8; Ell. N. A. Fung. 603; 
Ohio, James, Cheney; lowa, Macbride; Pennsylvania, Sumstine. 
Nigrofomes gen. nov. 
Hymenophore large, perennial, epixylous, sessile; context 
woody, purple, tubes cylindrical, stratose, thick-walled, black ; 
spores ovoid, smooth, hyaline. 
The type of this genus is Polyporus melanoporus Mont. (PI. Cell. 
Cuba, 422. 1842), found on trunks of trees in tropical America. 
The genus is readily distinguished from its near allies by its purple 
context and black tubes. 
Nigrofomes melanoporus (Mont.) 
Polyporus melanoporus Mont. Pl. Cell. Cuba, 422. 1842. 
This species is the darkest-colored of the perennial polypores. 
It was first described from collections made in Cuba by Ramon 
de la Sagra. Underwood has also collected it several times in 
Jamaica and Florida and Smith has found it in Nicaragua. It is 
probably more or less common throughout tropical America on 
decaying trunks of various broad-leaved trees. 
Poronidulus gen. nov. 
Hymenophore annual, tough, sessile, epixylous, at first sterile 
and cup-like, the fertile portion developing from’ the sterile ; con- 
text white, fibrous, tubes short, thin-walled, mouths polygonal ; 
spores ellipsoidal, smooth, hyaline. 
The type of this genus is Boletus conchifer Schw. (Syn. Fung. 
Car. 72. 1818), avery common and abundant species on dead elm’ 
branches. The development of the fruit-body is peculiar, being 
in two stages, the first ending with the formation of a cup-shaped 
Sterile body, from which the fruit-body proper later develops. 
This preliminary pileus begins as a knot of whitish mycelium, 
