Lichens marins - Myriolecis massei M. Bertrand & J.Y. Monnat

Myriolecis massei M. Bertrand & J.Y. Monnat

Myriolecis massei M. Bertrand & J.Y. Monnat

Description

Thallus crustose, 5-15 cm in diameter which can form large colonies, areolated, not warty and forming irregular polygonal areoles, this thallus sometimes being reduced to a few scales, dirty yellowish, yellowish gray, generally without a clearly demarcated prothallus on granitic rocks but sometimes gray-blue on less acidic rocks. Apothecia often numerous and scattered throughout the thallus, 0.3-0.6 cm in diameter, at first immersed in the thallus then sessile, disc flat to slightly convex, reddish-brown, brownish, margin concolor to the thallus, fine, sometimes slightly sinuous or crenellated. Amphithecium with POL+ crystals soluble in KOH and insoluble in N. Ascus clavate, 42-55 x 13-20 µm according to the literature, 40-50 x 17-27 µm according to our measurements. Elliptical spores, simple (but can appear 1-septate by the presence of 2 droplets), hyaline, 8-15 x 4-7 µm according to the literature, 11-15 x 5-7 µm according to our measurements. Frequent pycnidia visible by their brown ostiole, curved conidia, 19-32 x 1 µm. Cortex: C+ orange, K+/- yellow, KC+ orange, P-, medulla: C-, K+/- yellow, KC+ orange, P-; contains chlorinated xanthones. Relatively common species in the West of France on the more or less siliceous rocks of the mesic supralittoral zone, often in the company of Hydropunctaria maura s.l. and up to the level of Crithmum maritimum and Armeria maritima.

Easy to confuse with:

Myriolecis actophila with darker and almost blackish apothecia but especially with the C- thallus.

Myriolecis fugiens which is also C+ orange (but much more!) and whose general appearance is much more yellowish-brown and the thallus less bordered and which is P+ orange.

Myriolecis andrewii whose apothecia are P+ orange.

N.B. Quite variable species depending on its substrate, its position on the shore and its exposure to shade and sun, etc. however its chemical reactions to the usual reagents are determining.