British fungi - Keys

The genus Xanthoria - update in progress

1	Soredia absent	2
	Soredia present, situated on edge or underside of lobes	1. candelaria
2(1)	Thallus with narrow lobes, the apices up to 1 mm across	3
	Thallus with wide lobes, the apices (0·5–)1–7 mm across	4
3(2)	Thallus with finger-like, convex lobes spreading outwards beyond apothecia; on rock	2. elegans
	Thallus with finely divided lobe-ends often obscured by crowded apothecia; on bark and wood, rare on rock	6. polycarpa
4(2)	Lobes rounded at apices, scarcely indented; thallus of ± flat, regular rosettes	5
	Lobes strap-shaped, deeply divided; thallus often irregular, hummock-forming, of overlapping lobes	5. ectaneoides
5(4)	Thallus isidiate; isidia irregularly globose-capitulate, continuous; apothecia peltate, urceolate to concave, with involute thalline exciple	4. calcicola
	Thallus not isidiate, but sometimes with flattened lobules (on damaged thalli); apothecia ± sessile, usually with raised thalline exciple	3. parietina

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