Pyxine cognata Stirt. , Proc. Royal Phil. Soc. Glasgow

Mongkolsuk, Pachara, Meesim, Sanya, Poengsungnoen, Vasun & Kalb, Klaus, 2012, The lichen family Physciaceae in Thailand-I. The genus Pyxine, Phytotaxa 59 (1), pp. 32-54 : 42

6. Pyxine cognata Stirt., Proc. Royal Phil. Soc. Glasgow 11: 311 (1879).

Holotype:— INDIA. Nilgherries [Nilgiri]; A. Watt s. n. ( BM!).— Pyxine berteriana var. himalaica D. D. Awasthi, Phytomorphology 30: 366 (1982) . Holotype:— INDIA. Almora district; Uttar Pradesh, on way to Kasardevi , ca. 1930 m, on bark, 12 June 1956, D. D. Awasthi 3476 ( LWG!) .

Thallus corticolous, 2–6 cm wide, adnate to tightly adnate. Lobes radiating, discrete to ± contiguous, plane to slightly concave, in older thalli becoming slightly convex in the centre, 0.3–1.0 mm wide, subrotund to truncate at the apices. Upper surface white to whitish grey or grey-brown, pruinose in extended patches near the apices, the pruina ± glistening; polysidiangia, isidia and soralia absent. Pseudocyphellae not prominent, usually retricted to the margins, rarely laminal or becoming subreticulate, often obscured by spreading pruina. Medulla orange in upper part; lower medulla white. Lower surface black in the centre, paler towards the margin; rhizines ± dense, furcate. Apothecia common, obscurascens - type, 0.3–1.0 mm wide; disc epruinose. Internal stipe distinct, upper part orange-red, K + pale red, P-, C-, KC-, lower part much paler or white, K-, P-, C-, KC-. Ascospores (13–) 16–20 × 6–7 μm. Pycnidia not seen.

Chemistry: Cortex K-, UV + yellow; medulla K-, C-, KC-, P-; containing lichexanthone (major), terpenes (major or minor), unknown pigment (minor or trace).

Distribution and habitat:—Uncommon on bark in dry dipterocarp, dry evergreen and mixed deciduous forests. Also in Australia, China, India, Java and South America; not yet known from Africa.

Notes:— Pyxine cognata is characterized by the cortical lichexanthone, the absence of vegetative propagules, the partly orange medulla and apothecia of the obscuracens - type with an orange-red, K+ pale red internal stipe. Pyxine berteriana is similar, but it has broader, sparsely pruinose lobes and a medulla that is partly yellow. The two species contain very different arrays of terpenes ( Kalb, 1987, pl. 11).

Material from Thailand examined:— Chiang Mai; Queen Sirikit Botanic Garden, on Melia azedarach , hill evergreen forest, 1170 m, 30 June 1994, K . Boonpragob 2278 ( RAMK).— Chiang Mai; Queen Sirikit Botanic Garden , on Stereospermum neuranthum , dry dipterocarp forest, 730 m, 18°53'54'' N, 98°51'38'' E, 30 June 1994, K . Boonpragob 3582 ( RAMK).— Loei; Phu Luang Wildlife Sanctuary, Pak Dang Forest Ranger Station , on the bark of an unidentified tree in dry evergreen forest, 750 m, 17°10'42'' N, 101°21'48'' E, 22 May 2009, S . Meesim 259 ( RAMK).— Loei; Phu Luang Wildlife Sanctuary, Phu Ho Forest Ranger Station , on the bark of Tamarindus indica in mixed deciduous forest, 569 m, 17°07'13'' N, 101°34'30'' E, 29 July 2009, S . Meesim 338 ( RAMK).— Loei; Phu Luang Wildlife Sanctuary, Nam Chan Forest Ranger Station , on the bark of an unidentified tree in mixed deciduous forest, 397 m, 17°20'49'' N, 101°33'29'' E, 28 July 2009, S . Meesim 344 ( RAMK).— Loei; Phu Luang Wildlife Sanctuary, Nam Chan Forest Ranger Station , on the bark of Saraca indica in mixed deciduous forest, 397 m, 17°20'49'' N, 101°33'29'' E, 28 July 2009, S . Meesim 347, 348 ( RAMK).— Nakhon Ratchasima; Khao Yai National Park , on the bark of Roystonea regia in secondary forest, 385 m, 14°33' N, 101°40' E, 15 January 2000, N . Homchantara 16269 ( RAMK) .