Key to the species of Herpothallon known from China

1. Prothallus and pseudisidia with red pigment, K+ purple in pigmented parts.......................................................... H. rubrocinctum 1 Prothallus and pseudisidia without red pigment (rarely pinkish or lilac pigments present in pseudisidia) ....................................... 2

2. Thallus C+ red; gyrophoric acid major, lecanoric acid and some other substances minor ................................................................ 3 Thallus C–; gyrophoric and lecanoric acids absent............................................................................................................................ 5

3. Thallus K+ yellow; an unknown substance present (RF close to atranorin in solvent C) present; pseudisidia cylindrical (0.2 × 0.1 mm)............................................................................................................... H. viridi-isidiatum P.F. Chen & L.L. Zhang (2022: 07) Thallus K–; the unknown minor substance absent; pseudisidia globular or cylindrical .................................................................... 4

4. Pseudisidia globular (0.1 × 0.1 mm) ......................................................................................................................... H. subglobosum Pseudisidia cylindrical (1.0 × 0.1 mm).......................................................... H. philippinum (Vain.) Aptroot & Lücking (2009: 43)

5. Thallus K+ yellow or K+ yellow then red, P+ orange-red; stictic or norstictic acids present ........................................................... 6 Thallus K–, P– or P+ yellow; stictic and norstictic acids absent........................................................................................................ 7

6. Thallus K+ yellow then red; norstictic acid present; pseudisidia irregularly cushion-shaped (0.4 × 0.2 mm).......... H. capilliferum Thallus K+ yellow; stictic acid present; pseudisidia cylindrical (0.3 × 0.1 mm)................................................................................. ......................................................................................................................... H. polyisidiatum P.F. Chen & L.L. Zhang (2022: 02)

7. Thallus P–; psoromic acid absent ....................................................................................................................................................... 8 Thallus P+ yellow; psoromic acid present.......................................................................................................................................... 9

8. Confluentic acid major; globular pseudisidia (0.06–0.12 mm in diam.).................................................................... H. tomentosum Perlatolic acid major; minute, irregular, soredia-like granular pseudisidia (0.05 × 0.05 mm in diam.) .............................................. ....................................................................................................................... H. granulare (Sipman) Aptroot & Lücking (2009: 43)

9. Pseudisidia cylindrical (0.5 × 0.1 mm).......................................................................................................................... H. echinatum Pseudisidia subglobose to irregularly cushion-shaped ..................................................................................................................... 10

1 Wei J.C. (2020) The Enumeration of Lichenized Fungi in China. In: Beijing, China Forestry Publishing House, China, 44–47. Specimen examined: CHINA. Guizhou Province: Leishan County, Leigongshan National Forest Park, 892 m elev., on bark of a tree, 2 Nov. 2009, Q. Tian, 20102819 (SDNU). Discussion: The identification of this material as Herpothallon rubrocinctum appears problematic, because its prothallus is an orange to red (rather than bright scarlet red), the thallus lacks secondary metabolites and the pseudisidia of the specimen are granular. Molecular data could not successfully be obtained from the material. The report of H. rubrocinctum may thus refer to a still undescribed species, which needs to be further investigates, when fresh specimens are collected.

10. Pseudisidia without pinkish or lilac pigments; subglobose (0.22–0.3 × 0.11–0.18 mm)............................................ H. glaucescens Pseudisidia with pinkish or lilac pigments; subglobose to mostly irregularly cushion-shaped ....................................................... 11

11. Thallus tightly appressed, medulla I–; pseudisidia irregularly cushion-shaped, pinkish, large (1 × 0.5 mm) ......................... H. weii Thallus loosely appressed, medulla I+ blue; pseudisidia whitsh subglobose or irregularly cushion-shaped, basally white, upper parts often lilac to lilac grey, small (0.1–0.45 mm in diam.)........................................................................................... H. lilacinum