Life habit: lichenized Thallus: crustose, leprose or byssaceous, in rounded patches or irregularly spreading, indeterminate to determinate, unstratified or stratified; prothallus: not evident surface: bright yellow to vivid yellowish green, entirely composed of soredia and/or anastomosing hyphae soredia: spherical, fine (up to c. 50 Ám in diam.) to coarse (mostly more than c. 50 Ám in diam.), loosely constructed and easily becoming disintegrated in squash preparations photobiont: primary one a Chlorophyceaen coccoid (up to 22 Ám in diam.), secondary one absent Ascomata: apothecioid, rare, immersed or superficial, up to 2 mm in diam., round disc: green, yellow, pale orange or brownish; concave to spherical margin: poorly developed and ecorticate, or absent exciple: poorly developed, composed of anastomosing hyphae epihymenium: distinct, composed of the upper parts of the paraphysoids hymenium: up to 75 Ám tall; hamathecium: composed of paraphysoids richly anastomosing in epihymenium, without or with only slightly swollen apical cell; hypothecium: hyaline, poorly developed asci: clavate, the inner wall extends to form a K/I+ blue papilla, 8-spored ascospores: hyaline, 3-septate, narrowly obovate to narrowly ellipsoid, 9-15 x 2.5-5 Ám Conidiomata: unknown Secondary metabolites: pulvinic acid derivatives, terpenes, depsides, and diagnostic unknowns Geography: world-wide on all continents Substrate: on trees, wood, rock, and plant remnants. Note: Prior to the discovery of ascomata (Laundon 1981), species of Chrysothrix were placed in Lepraria, a genus for which no ascomata are known.