1920] 



BURT THELEPHORACEAE OF NORTH AMERICA. XII 



191 



_4i 



^2 



ju; colored 

 yu sometimes 

 zones of the 



Fig. 30. S. amhigxmm. Section of 

 hymenial region X 68; peripheral part 

 of cystidium, c, and spores, s, X 650. 



even, 10-13 X3f 

 spores 12X3M 

 occur in deeper 

 hymenium. 



Resupinate part 1-8 cm. long, 

 1-4 cm. wide, reflexed part 1-5 

 mm. broad in the only reflexed 

 specimen known. 



On logs of Abies and, perhaps, 

 Pinus Strobus. Vermont and 

 New York. June to November. 

 Very rare. 



S. ambiguum belongs in the 

 group of species with S. abietinum 

 and S. rugisporum on account 



of similarity in microscopic structure including the colored 

 cystidia. It may be separated from both these species at sight 

 by the color of its hymenium which is permanently umber and 

 not at all cinereous nor glaucous. There is a difference in 

 chemical composition also, for dilute potassic hydrate solution 

 blackens the sections and becomes itself discolored as in the 

 case of species of Hymenochaete. In fact, the general aspect 

 of resupinate, thick, mature, deeply cracked specimens is very 

 like that of Hymenochaete spreta — a species which occurs only 

 exceptionally on a coniferous substratum. It is possible that 

 S. ambiguum occurs in reflexed form in the state of Washing- 

 ton, for the collection cited under S. rugisporum, Olympic 

 Mts., T. C. Frye, 1, resembles S. ambiguum but is not quite in 

 perfect enough condition for confident reference here. 



Specimens examined: 

 Vermont: Middlebury, C. G. Lloyd, 10652 (in Lloyd Herb, and 

 Mo. Bot. Card. Herb., 44585); Ripton, E. A. Burt; Smug- 

 glers Notch, Mt. Mansfield, E. A. Burt. 

 New York: Adirondack Mts., C. H. Peck, type (in N. Y. State 

 Mus. Herb.) ; Averyville, C. H. Peck (in N. Y. State Mus. 

 Herb, and Mo. Bot. Gard. Herb., 55699). 



59. S. umbrinum Berk. & Curtis, Grevillea i: 164. 1873; 

 Wakefield, Kew Bui. 1915:369. 1915. — CoTd^SiXQ Stereumumbri- 



