Santessoniella rosettiformis, a new species from South America with notes on S-pulchella (Pannariaceae)

The new species Santessoniella rosettiformis Henssen is described from a te mperate Nothofagus forest in southern Chile and compared with the superfici ally similar S. pulchella P. M. Jorg. In both species, the thallus is corti cate on all surfaces, the characteristic feature separating Santessoniella from Parmeliella. In the blue iodine reaction of the hymenium and the prese nce of smooth spores, S. rosettiformis corresponds to the closely related S . chilensis (Hue) Henssen whereas S. pulchella with warty spores and reddis h brown hymenium in iodine is related to S. polychidioides (Zahlbr.) Hensse n, the type species of the genus. A key to the species of Santessoniella is provided; the delimitation of the genus is discussed. (C) 2000 The British Lichen Society.