Three new species of <i>Agaricus</i> from Baiyun Mountain, Guangzhou, China

<i>Agaricus</i> is a species-rich genus with more than 600 species around the world. In this work, three new species, <i>Agaricus cacainus, A. baiyunensis</i>, and <i>A. praeclarefibrillosus</i> are described from the specimens collected at Baiyun Mountain, Guangzhou, China, a subtropical area with a monsoon maritime climate, based on phylogenetic analyses and morphological examinations of internal transcribed spacer (ITS1-5.8S-ITS2 = ITS), D1/D2 domains of the large subunit of ribosomal DNA (28S), and a part of translation elongation factor 1-alpha (<i>TEF1</i>). <i>Agaricus cacainus</i> in <i>A</i>. sect. <i>Amoeni</i> is characterized by a parabolic to applanate, slightly depressed pileus covered with chocolate brown, appressed, triangular squamules against white background, a white, furfuraceous stipe, an unchanging context when cut, a fragile and evanescent annulus, usually 4- or 2-spored basidia, and mostly pyriform cheilocystidia. <i>Agaricus baiyunensis</i> in <i>A</i>. sect. <i>Minores</i> has a pileus with a slightly truncate top covered with light brown, downy-wooly fibrillose scales and a light yellowish stipe with membranous annulus. <i>Agaricus praeclarefibrillosus</i> in <i>A</i>. sect. <i>Brunneopicti</i> is characterized by a pileus surface with brownish, triangular, recurved scales and longitudinally splitting lines toward margin, a cottony stipe with white, tiny, recurved fibrils, a single annulus, and variously shaped cheilocystidia, with sparsely ornamented basidiospores. The detailed comparison of their morphological characteristics with closely related species is provided.