Thallus corticolous, rarely saxicolous or foliicolous, delimited by a distinct byssoid prothallus of carmine red, radiating hyphae; thallus surface grayish to greenish white, ecorticate, dense, cottony, felt-like, in the center covered by carmine red, granular pseudisidia; medulla white, in parts filled with carmine red granules and sparse calcium oxalate crystals (insoluble in KOH, forming colorless, needle-shaped crystals in 25% H2SO4); asci and pycnidia not observed.

Spot tests and chemistry: P-, K- (green thallus areas), K+ purple (carmine red prothallus & pseudoisidia), C-, KC-; UV- (dull), ILugol’s-; confluentic, chiodectonic, 2'-O-methylmicrophyllinic acids.

Distribution and ecology: Cosmopolitan; by far the most common Herpothallon species in Galapagos, often very abundant and sometimes forming thalli of several decimeters across; common in the humid and upper transition zone, rarely also in the dry zone, on a wide variety of both native and introduced tree species, rarely also on rock; both in sunny, exposed and ±shaded and sheltered habitats.

Selected specimens examined: Ecuador: Galapagos: Isla Fernandina, W-side, alt. 335m, transition zone, Cavagnaro, D. s.n. (COLO 193387, L-40446). Isla Floreana, ca. 1 km S of Cerro Verde, 1°18’34”S, 90°25’19”W, alt. 299m, transition zone, on bark, 15-Jan-2011, Yánez 1945 (CDS 48297). Isla Floreana, trail going to Post Office Bay off the dirt road between highlands and Puerto Velasco Ibarra, 1°17’17”S, 90°26’35”W, alt. 360m, transition zone, on bark, 14-Jan-2011, Yánez 1921 (CDS 48275). Isla Pinta, along the trail up to the summit from the S-coast, 0°34’39”N, 90°45’7”W, alt. 436m, humid zone, on bark, 27-Feb-2007, Bungartz 5828 (CDS 33501); 0°34’34”N, 90°45’8”W, alt. 414m, transition zone, on bark, 25-Feb-2007, Bungartz 5735 (CDS 33378); northern part of the western cliff above Las Pampas, 0°35’11”N, 90°46’34”W, alt. 356m, dry zone, on bark, 31-Jan-2008, Nugra 606 (CDS 38984). Isla Pinzón, summit, transition zone, on bark, Cavagnaro, D. s.n. (COLO 192819, L-40489). Isla San Cristóbal, Bailey s.n. (COLO 151174, S-27084); along trail between entrance to Cerro Pelado and Cerro Partido, trail to El Ripioso, 0°51’40”S, 89°27’38”W, alt. 383m, transition zone, on bark, 28-Apr-2007, Bungartz 6678 (CDS 34914); along trail to Ochoa, along the northern border of the National Park, 0°53’39”S, 89°33’19”W, alt. 315m, humid zone, on bark, 24-Aug-2008, Herrera-Campos 477 (CDS 43368). Isla Santa Cruz, above the Finca of Galo Torres, inside the Park boundary, 0°37’45”S, 90°24’1”W, alt. 536m, humid zone, on bark, 30-Jun-2006, Bungartz 4993 (CDS 29206); along the dirt road from Bellavista to Media Luna, farmland on the W-side of the road, 0°40’54”S, 90°19’26”W, alt. 285m, humid zone, agricultural area, on bark, 28-Feb-2006, Bungartz 3989 (CDS 27919); along the road from Bellavista to Los Gemelos, 0°38’10”S, 90°23’45”W, alt. 579m, humid zone, on bark, 12-Feb-2006, Bungartz 3476 (CDS 27232), Bungartz 3493 (CDS 27249), Aptroot 63866 (CDS 30424). Isla Santiago, E of salt lake at Santiago Bay, 0°14’25”S, 90°48’50”W, alt. 170m, dry zone, on bark, 30-Apr-1971, Pike 2707 (COLO 263253, L-56175), Pike 2707 (OSC 54834); summit of Cerro Gavilan, inner N- and NE-exposed crater rim, 0°12’20”S, 90°47’3”W, alt. 840m, humid zone, on rock, 23-Mar-2006, Aptroot 65753 (CDS 32345); on bark, 03-Jan-1906, Stewart 3446 (FH 197182). Isla Isabela. Volcán Alcedo, outer SE-exposed slope and crater rim, 0°27’29”S, 91°7’19”W, alt. 1089m, humid zone, on bark, 05-Mar-2006, Bungartz 4041 (CDS 27971), Bungartz 4241 (CDS 44660); lower crater slopes above the first Caseta del Parque; below the cloud layer, 0°58’37”S, 91°25’26”W, alt. 456m, humid zone, on bark, 03-May-2012, Nugra 1036 (CDS 52200);; Volcán Sierra Negra, along dirt road from Puerto Villamil to crater of Sierra Negra, farmland, 0°50’38”S, 91°3’52”W, alt. 564m, humid zone, on bark, 09-Sep-2007, Bungartz 6891 (CDS 36379); Cueva del Sucre, at the entrance (parking), SE side of the island, 0°50’33”S, 91°1’37”W, alt. 369m, humid zone, on bark, 15-Aug-2008, Herrera-Campos 10644 (CDS 40381).

from:
Bungartz, F., Dútan, V. & Elix, J.A. (2013) The lichen genera Cryptothecia, Herpothallon and Helminthocarpon (Arthoniales) in the Galapagos Islands, Ecuador. The Lichenologist 45(6): 1–24.