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This booklet provides information on lichens in general and more specifically on the lichen biota of the Namib Desert, with 75 species illustrated in colour, enabling the user to identify most of the lichens occurring there.

Example: Caloplaca namibensis

Kaernefelt

Thallus orange to orange-red, crustose, rosette-forming, consisting of radially arranged, long, narrow lobes, in age central parts often occupied by short, irregularly arranged lobes, 1-3(-5) cm diam.

Lobes cartilaginous, hard, convex or flat, tightly adnate, but older parts in central portions of the thallus becoming raised and ascending towards the centre, sparsely dichotomously branched, 0.3-0.5(-0.8) mm broad, up to 25 mm long, mainly in central portions covered by isidia; short accessory lobules developed on lobe margins. Isidia simple to coral-loid. Amorphous epinecral layer above cortex 10-20 um thick. - Apothecia not observed.

Reactions/chemistry: all parts K+ purple; anthraquinones.

Habitat/distribution: nearly exclusively on quartz pebbles, in fairly dry habitats, from northern to southern Namib; endemic to south-western Africa.

Remarks: Very similar is C. elegantissima, which is distinguished by the lack of isidia and the frequent presence of apothecia (at least in older thalli), furthermore by more separated, broader and thicker lobes, whereas the lobes of C. namibensis usually (not always!) are contiguous. C. namibensis is confined to quartz pebbles/stones; occurrence on magmatic rock (dolerite) is quite unusual; less drought-resistant than C. elegantissima. Differs from Xanthoma species in lacking a lower cortex and is not being readily separable from the substrate. Picture: section 2.6 cm wide.