Sticta key
| Key adapted from Magain & Sérusiaux (2015) | ||
| 1 | Photobiont green algae, sometimes in small lobes developing from a cyanobacterial morph | Sticta canariensis |
| Photobiont cyanobacteria | 2. | |
| 2 | Thallus sorediate, soralia formed especially at the margins; with rather large, suborbicular lobes with plane and undulating margins | Sticta limbata |
| Thallus with isidia, sometimes also with phyllidia | 3. | |
| 3 | Thallus with the upper surface strongly maculate; margins often strongly dissected and fragmenting, with phyllidia always present at the margin and usually also on the upper surface | Sticta canariensis |
| Thallus smooth or scrobiculate, but not strongly maculate; isidia present and often copious, usually coralloid | 4. | |
| 4 | Surface cells of cyphellae distinctly papillate | 5. |
| Surface cells of cyphellae smooth, papillae rare or completely absent | 6. | |
| 5 | Thallus rather robust, rounded, monophyllous (and then typically mushroom-like) or with several rounded lobes, hardly dissected, dark brown, rarely pale greyish; margin typically involute, rarely sparsely ciliate on regenerating lobules; papillae on cyphella membrane few per cell; apothecia rare | Sticta fuliginoides |
| Thallus very fragile and easily broken when dry, rounded to palmate, with lobes rounded (when young) to truncate (when old), dark dull brownish, lead grey or pale greyish; margin usually not involute, usually ciliate, especially when young; papillae on cyphella membrane numerous per cell, easily seen in fresh material; apothecia present in well-developed specimens, typically ciliate | Sticta ciliata | |
| 6 | Thallus distinctly branched, almost always dichotomously, typically glossy; lobes involute, shallow and usually with ascending margins; lower surface usually dark, especially towards the centre, strongly contrasting with the white cyphellae | Sticta sylvatica |
| Thallus not distinctly branched, although lobes can be lacerate or dissected, not typically glossy; lobes rounded; lower surface usually pale or brownish, not strongly contrasting with the white cyphellae | 7. | |
| 7 | Lobe surface with distinct swellings, irregular in shape but always present, with isidia developing on their upper parts | Sticta atlantica |
| Lobes surface with no or irregular swellings, but rather typically reticulate or scrobiculate, and isidia developing on the edges of these dimples | Sticta fuliginosa | |