Herteliana gagei (Sm.) J. R. Laudon
Herteliana taylori (Salwey) P. James
Thallus crustose, superficial, to 25 cm across, smooth or minutely rimose-cracked notably towards the center, typically blue-green in the shade, 'duck egg colour' or pale grey-glaucous to grey-bluish or whitish-yellowish in eroded places, creamy white and white-greyish in places slightly exposed to direct light, prothallus more or less distinct, except in case of mosaics, then black and delimiting. Thalli are most often located at the base of rocks in contact with the ground, seldom isolated at mid-air on rocks except close to stream banks or ever humid rocks. Three main morphs (and all intermediate specimen) may be found: (i) the more or less fertile on damp rocks constantly moist in shaded woodlands (for more details see Herteliana gagei fertile form), (ii) the sterile morph on less humid rocks with limited shade most often on rocks and large stones of forest pathes (see Herteliana gagei saxicolous form) and (iii) the pycnidiate form (Herteliana gagei pycnidiate form). A fourth sorediate form may also be found (see later). In fertile form, apothecia are immersed at first, becoming sessile by rupture of the thallus, 0,5-0,7 mm diam., convex to tuberculate, often circled with a remaining ring of thallus more or less torn and with purple halo, disc dark brown-red (this form is rather rare and most often, apothecia development is uncomplete). Ascospores simple, fusiform with pointed ends, 18-22 x 8-10 µm. Pycnidia usually numerous, minute cone-shaped, crater on top. Photobiont: Chlorococcoid. Thallus C-, K+ yellow, KC+ yellow, Pd-. Common species growing at the base of siliceous rocks and in contact with the ground in humid oceanic heathlands where it is a good marker of primal Atlantic forest. Rare at the shaded base of old moist walls, common on rocks in woodlands and oceanic forests. N.B. It seems that the specimen collected in our propection area in highly exposed aerohaline heathlands, sterile and moderately sorediate, correspond to sorediate samples collected in Cape Lizard. See Herteliana gagei saxicolous form of exposed seashores.