1916] 



BURT THELEPHORACEAE OF NORTH AMERICA. V 751 



differences in regard to whether the hyphae are crowded close 

 together or are loosely arranged. Under c, a conspicuous 

 example would be one in which the layer next to the sub- 

 stratum is composed of longitudinally arranged hyphae (that 

 is, parallel with the substratum) crowded closely together; 

 from this layer, a few branches might extend outward at right 

 angles to the first layer and form a layer of loosely arranged, 

 erect hyphae the second layer; the hyphae of the second 

 layer might branch abruptly at its outer surface and bear a 

 compact hymenial layer. Some species invariably form a 

 loosely interwoven layer next to the substratum, and on the 

 surface of this layer form a dense hymenial layer, as, for ex 

 ample, Sehacina incrustcms, S. chlorascens, and 8, Helvel- 

 loides. Sterile fructifications may frequently be determined 

 by their general characters and structure in section. 



The preparations which reveal structure in section, give also 

 spores, basidia, paraphyses, and other organs. From the 

 combination of general characters, structure in section, and 

 details of spores and noteworthy organs, the species becomes 

 manifest. Our species of Sehacina are described in accord- 

 ance with this method in the following pages. 



Key to the Species 



Fructifications on the earth, running up and incrusting the bases of living 



stems and trunks as well as dead objects 1 



Fructifications confined to bark and wood of dead branches and trunks ... 2 



1. Sometimes passing into branches or ascending flaps; hymenial layer drying 

 warm buff, 60-150 fi thick; paraphyses densely crowded and somewhat 

 interwoven or adglutinated 1. 8. incrustana 



1. Pileate branches drying cream-color with a glaucous tint, imbricated, the 

 apices spiculose or fimbriate; hymenial layer dryihg vinaceous brown, 

 140-240 /* thick 3. S. chlorascens 



1. Not forming free branches or flaps; hymenial layer 200-300 /x thick; 



paraphyses straight and rod-like; basidia 20-25X15 /t 4- S. Helvelloides 



2. Fructifications white or whitish when dry 3 



2. Fructifications not white 4 



3. Hymenium composed of unbranched, flexuous, even-walled, deeply staining, 

 clavate organs 40-45X6 fi, in addition to few-branched paraphyses and 

 basidia 5. 8. 8hearii 



3. Hymenium composed of paraphyses and basidia; fructification 300-400 fi 



thick ; margin thick, not closely adnate to substratum 6. 8. macrospora 



3. Hymenium composed of basidia and paraphyses; fructification 50-150 n 



thick, shining white at first; margin very thin and closely adnate. .7. 8. calcea 



3. Hymenium composed of basidia and paraphyses; fructification 200-300 fi 

 thick, dirty whitish; hyphae incrusted in upper two-thirds of fructifica- 

 tion; margin thin and closely adnate 8. 8. monticola 



