Overholts: Diagnoses of American Porias 11 



the fructification I find the spores as described. My sectional 

 preparations have been exhibited to other members of the Botany 

 Department at this institution and all have agreed that no other 

 interpretation is possible. On the other hand, I have repeatedly 

 demonstrated the connection of the globose spores of P. nigresccns 

 with their basidia (Fig. 6, c). Consequently these plants can not 

 represent the same species, although so similar that at present the 

 writer is not aware of any separating characters other than the 

 spores and the basidia. The basidia of P. nigrescens are large, 

 5-7 jx in diameter, while those of P. odora are much smaller, only 

 2-4./*. 



I have not recently examined P. broomei as distributed by 

 Rabenhorst (Fung. Eur. 2004), and specimens are not at present 

 available. My judgment would be, however, that it represents 

 what I have previously referred to Poly poms rigidus Lev. This 

 plant is only rarely pileate, and when resupinate I find it very 

 difficult to distinguish, microscopically and macroscopically, from 

 thin light-colored forms of P. nigrescens. • 



State College, 



Pennsylvania. 



Explanation of Plate I 



Fig. 1. P. nigrescens. Microphotograph of cross-section of hymenium, 

 X 160. 



Fig. 2. Same, X 320, showing the absence of basidia in well-developed 

 specimens ; also the peculiar thick-walled hyphae that give a pseudo-cellular 

 appearance to the trama. 



Fig. 3. P. ferruginosa. Microphotograph of cross-section of the hymenium, 

 X 160, showing the abundant setae. 



Fig. 4. Same, X 320, showing the setae. 



Fig. 5. P. amb'xgua. Microphotograph of cross-section of the hymenium, 

 X 160. 



Fig. 6. Same, showing the occasional cystidia as at a. 



