1920] 



BURT THELEPHORACEAE OF NORTH AMERICA. XII 



193 



Fig. 31. S. umhrinum. Section of hyme- 

 nial region X 488, showing z, cystidia. 



hyphae and curve outward 

 through the hymenium 

 as sharp-pointed cystidia, 

 even, rough-walled, or in- 

 crusted, 100-200X6-10 Ai, 

 protruding up to 40 /x; spores 

 white in spore collection, 

 even, 6X3| ix. 



Resupinate on areas 1-3 

 cm. in diameter, becoming 

 laterally confluent for 10-15 

 cm., reflexed portion 2-5 

 mm. broad. 



On fallen limbs of oak, 

 hickory, and other fron- 

 dose species. North Caro- 

 lina to Texas and south- 

 ward from Ohio and Illinois, in Arizona, West Indies, and 

 Central America; occurs also in Poland, Cochin China, and 

 Australia. September to February, but collected occasionally 

 in the other months of the year. 



S. umhrinum may be recognized by the purple color of young 

 specimens which fades or changes finally to snuff-brown, al- 

 though usually showing a vinaceous tinge, and by its remarkable 

 cystidia, which, on account of their color and lack of conspicuous 

 incrustation, verge towards setae. However, these organs are 

 paler colored and much more elongated than undoubted setae; 

 furthermore, sections of fructifications in which these colored 

 cystidia are present do not immediately darken when dilute 

 potassium hydrate is brought in contact with them, as inva- 

 riably happens to sections containing true setae. It has seemed 

 best to retain for this species the name Stereum umhrinum B. & 

 C, because the type of Stereum umhrinum Fr., Herb. Preiss., 

 No. 2686, collected in Australia on Banksia Menziesii, must be 

 found and studied to complete the Friesian description before it 

 can be known whether the Preiss specimen is not really a 

 Hymenochaete, Eichleriella, Auricularia, or, perhaps, even identi- 

 cal with S. umhrinum B. & C, a common species in Australia. 

 The presence of a white, intermediate layer seems to preclude the 



