Scutellinia key

Key adapted from an unpublished document by Yi-Jian Yao (Kew)
1 Fully developed ascospores globose to subglobose (ratio of length to breadth 1.0 - 1.2); ornamentation on ascospore surface very conspicuous 2
Fully developed ascospores broadly ellipsoidal to ellipsoidal (ratio of length to breadth greater than 1.2); ornamentation on ascospore surface conspicuous or not 6
2 Spore ornamentation comprising ± cylindrical or conical, truncate or pointed projections, often higher than 2 µm; ascospores less than 20 µm diam. 3
Spore ornamentation comprising mainly hemispherical warts, mostly lower than 2 µm high, or if higher than 2 µm then ascospores greater than 20 µm diam. 4
3 Spore ornamentation of conical projections, pointed at the apex; marginal hairs of apothecium with 3 - 5 septa; ascospores 15.5-18 µm diam. S. legaliae
Spore ornamentation comprising truncate, rarely pointed, almost cylindric or tapering projections; marginal hairs of apothecium commonly with many septa; ascospores 14-17 µm diam. S. trechispora
4 Ascospores (23-) 24-30.5 (-33) x (22-) 23.5-30.5 (-33) µm; spore ornamentation of large warts, commonly 2-3 (-4) µm high and 2-4 µm broad, interspersed with small punctae S. citrina
Ascospores usually less than 23 µm diam., never greater than 25 µm diam.; spore ornamentation lower than 2 µm high 5
5 Ascospores globose, 17.5-22 (-24.5) µm diam.; spore ornamentation varying in size, warts (0.5-) 1-1.5 (-3) µm across, (0.5 -) 0.8-1.2 (-1.8) µm high, frequently unevenly distributed; asci 20-32 µm diam. S. barlae
Ascospores globose to subglobose, 15.5-18.0 x 15.0-18.0 µm; warts (0.5-) 0.8-1.5 (-2) µm across, (0.5-) 0.8-1.5 (-1.8) µm high, usually evenly distributed; asci 18-22 µm diam.   S. minor (cf. also S. patagonica)
6 Fully developed ascospores 18-21 x 10-12 µm, smooth (at least as observed under the light microscope, x 100 oil lens); apothecia small, 0.5-1.5 (-2.5) mm diam. S. setosa
Fully developed ascospores ornamented (ornamentation discernible under the light microscope, x 100 oil lens); apothecia usually larger than 1.5 mm diam. 7
7 Spore ornamentation appearing as a complete or incomplete network in surface plan view 8
Spore ornamentation consisting of isolated warts or of short, sometimes irregular or interconnected ridges 9
8 Spore ornamentation of large warts, (0.8-) 1.5-2 (-3) µm  across and (1.5 -) 2 (-2.5) µm high, with narrow interconnections; ascospores broadly ellipsoidal or occasionally subglobose, 20-22.5 (-24) x 14-18 µ S. decipiens
Spore ornamentation reticulate in plan view, 0.5-1 µm across and 2.5-4 µm high, sometimes appearing as acuminate spines on spore outline; ascospores ellipsoidal, 17.5- 20 x 11.5-13 µm S. pseudotrechispora
9 Marginal hairs mostly dark, but sometimes almost colourless except near the base, short, mostly 150-200 µm long; spore ornamentation of small, isolated warts, 0.5-1 µm across and less than 0.5 µm high, sometimes mixed with short ridges; ascospores mostly broadly ellipsoidal, 20-25 x 14.5-20 µm S. kerguelensis
Marginal hairs uniformly dark yellow-brown or if pale then longer than 200 µm and/or spore ornamentation higher than 0.5 µm; spore ornamentation of isolated warts or of short interconnected ridges; ascospore shape various 10
10 Spore ornamentation appearing as short, interconnecting ridges 11
Spore ornamentation of predominantly isolated warts 15
11 Spores with an outer layer (including the ornamentation) that loosens when heated in lactic acid/cotton blue 12
Spores without a separable outer layer 14
12 Ascospores 23-28 x 11-14 µm; spore ornamentation 0.5-0.8 µm high on spore outline S. mirabilis
Ascospores less than 25 µm long, ellipsoidal to broadly ellipsoidal 13
13 Ascospores 19-24 x 11-15 µm; marginal hairs 150-400 µm long, often ± hyaline and curved in the upper part S. superba
Ascospores 15.5-19 x 8-11.5 µm; marginal hairs brown and flexuous throughout S. torrentis
14 Ascospores 17.5–22 (-23) µm long [to 13 µm wide]; marginal hairs often longer than 1000 µm, sometimes  1500-2000 µm long S. scutellata
Ascospores 21.5-28 µm long, mostly longer than 22 µm; marginal hairs usually shorter than 1000 µm S. olivascens
15 Spore ornamentation higher than 0.5 µm, distinctly visible on spore outline (under x 40 objective of the light microscope), often broader than 0.8 µm, reaching 2.5 (-4) µm across 16
Spore ornamentation usually lower than 0.5 µm, indistinct on spore outline, mostly less than 0.8 µm across 18
16 Ascospores ellipsoidal to broadly ellipsoidal, occasionally subglobose (ratio of length to breadth 1.2 - 1.6), (17.5 -) 18-22.5 (-24) x 13-17 µm S. umbrorum
Ascospores ellipsoidal or elongate-ellipsoidal (ratio of length to breadth 1.6 - 2.3), (21.5 -) 22.5-27.5 (- 31.5) x (10-) 11-13 (- 15.5) µm 17
17 Marginal hairs 18.0-25.0 µm diam.; ascospores equilateral, 25-27.5 x 12- 13 µm; spore ornamentation of conspicuous warts 0.8-1.2 (- 2) µm diam., occasionally confluent S. macrospora
Marginal hairs 20-50 µm diam.; ascospores frequently inequilateral, (21.5-) 22.5-26.5 x (10-) 11-13 (- 15.5) µm; spore ornamentation of warts varying in size, (0.3-) 0.5-1.5 (-2) µm across S. cejpii
18 Ascospores ellipsoidal (ratio of length to breadth 1.3 - 1.8), (19.0-) 20-23 (-24) x (12-) 13-15 (-16) µm; marginal hairs usually uniformly coloured; colourless and thin-walled hairs often also present S. subhirtella
Ascospores broadly ellipsoidal to ellipsoidal (ratio of length to breadth 1.2 - 1.3), 18.5-21 (-23.5) x 14.5-18 (-21) µm; marginal hairs pale at apex; colourless hairs absent S. patagonica

Taxonomic term: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith