Overholts: Diagnoses of American Porias 3 



peculiar shape of these tubes with their finely ciliate-dentate walls 

 is a distinct aid in recognizing the plants in the field. 



Internally the structure of the plant recalls that of Polyporus 

 pargamenus Fr., although striking microscopic differences are not 



Fig. 2. P. ambigua. a, Specimen collected and photographed by Dr. A. 

 H. W. Povah, Syracuse, N. Y., showing how the plant may grow around 

 grasses, twigs, etc. (Overholts Herb. No. 5351.) b, Resupinate specimen on 

 bark of Fagus. (Overholts Herb. No. 247.) X 1. 



lacking. Plants in all stages of maturity show an abundance of 

 oblong-ellipsoidal spores that measure 4-6x2.5-3.5^ (Fig. 1, d). 

 Their abundance suggests the possibility of their being conidial, 

 but in sections of the hymenium it is not difficult to trace their 

 connection to normal four-sterigmate basidia. Even a crushed 

 preparation of the hymenium yields an abundance of spores. There 

 are usually no cystidia to be seen, but prolonged search will some- 

 times yield inconspicuous conical or crystalline-capitate bodies, 

 scarcely projecting beyond the basidia (PI. I, fig. 6, a), and at 

 first sight not readily distinguished from the latter. They are 

 about 6 fx in diameter. The hyphae form a distinctive character 

 of the species (Fig. 1, a-c). They are long and flexuous, with 

 cross walls but no clamp connections, and are considerably 

 branched. Those of the subiculum are more branched than those 

 in the trama, have more frequent cross walls, and reach larger 



