252 POLYPOREAE OF SOUTH AFRICA. 



The basic idea of the genus Polyporus is that its members have 

 only a single layer of pores (distinguish from Font ex) which are 

 sunk in the context to equal depths (distinguish from Trametes). 

 Fomes spp. showing only the first year's pores may be mistaken 

 for a Polyporus. Some of the species of Polyporus (e.g., P. gilvus, 

 P. fructicum) may survive a few seasons, but they are never 

 typically perennial. Some species grade into Trametes, and it 

 may not always be easy to decide whether a specimen is a Polyporus 

 or a Trametes (cf. P occidcntalis, Tr. protea, and others). In 

 P. arcularius we find large favoloid pores suggesting the genus 

 Favolus, from which however it differs in having its stipe central. 

 In P. occidentalis and others a daedaloid tendency of the hymeuo- 

 phore may be at times met with. 



KEY TO THE SPECIES. 



Context white or light coloured. Series I. 



Context red or yellow. Series II. 



Context some shade of brown. Series III. 

 an elastic membrane. 



Series I. 

 Context white or light coloured. 

 1. Pileus stipitate. 



2. Stipe arising from a true or "false" sclerotium. 



3. A true sclerotium present. P. sacer 1 



3. Sclerotium "false" composed of agglutinated soil 



particles. P. arenosobasus 32 



2. Stipe not arising from a sclerotium. 



4. Stipe lateral. 



5. Spores truncate, coloured. 



6. Plant epixylous, surface laccate, reddish brown. 



P. lucid us 37 



6. Plant terrestrial, deeply rooted, surface laccate and 



black in mature specimens. P. nir/rolucidus 35 



5. Spores hyaline, not truncate. 



7. Surface of pileus black. P. dictyopus 2 

 7. Surface of pileus brown, azonate. P. varius 3 

 7. Surface of pileus yellow, or brown, zoned, pores 



minute. P. luteus 24 



7. Surface of pileus yellow, orange or white; plants 



densely imbricate, large, flesh v ; context of a cheesy 

 consistency and friable when dry. /'. sulphureus 33 



4. Stipe central or more or less excentric. 



8. Spores hyaline, not truncate. 



9. Pores large, radially elongated, stipe central, margin of 



pileus ciliate. P. arcularis 4 



9. Pores minute, round, stipe central or excentric, surface 



of pileus with multicoloured zones. P. xanthopus 5 



8. Spores coloured, truncate. 



