Hemigrapha (Müll. Arg.) R. Sant. ex D. Hawksw., Kew Bull. 30(1): 9 (1975).
≡ Melanographa sect. Hemigrapha Müll. Arg., Flora, Regensburg 65(33): 519 (1882).
Biotrophic on thallus of lichens. Sexual morph: black, superficial, roundish, stellate or elongate thyriothecioid ascomata. Upper ascomatal wall composed of a single layer of more or less parallel, radiating rows of dark reddish-brown cells, K+ dark olivaceous brown, often breaking by irregular cracks around the ostiole; a missing lower ascomatal wall. Hamathecium composed of sparingly branched and rarely anastomosed paraphysoids disappearing when over-mature and 0(−1)-septate periphysoids arising from the upper ascomatal wall, I–. Asci clavate to subglobose 4–8-spored asci, wall apically thickened with a distinct ocular chamber, I–. Ascospores 1–3-septate, constricted at the septa, hyaline and smooth when young, becoming brown, verrucose when over-mature. Asexual morph: pycnidial anamorph macroscopically indistinguishable from ascomata, with conidiogenous cells arising directly from the ascomatal wall and hyaline, aseptate, smooth, basally truncate conidia of two types, narrowly ellipsoid to rod-shaped microconidia and larger, ellipsoid macroconidia (Adapted from Diederich and Wedin 2000).
Type species: Hemigrapha asteriscus (Müll. Arg.) R. Sant. ex D. Hawksw.
Notes: Hemigrapha was introduced by Hawksworth (1975) with H. asteriscus as type species. Hemigrapha is characterised by solitary to gregarious ascomata, clavate to cylindric-clavate, subglobose asci and brown, ellipsoid, 1-septate ascospores (Diederich and Wedin 2000). Diederich and Wedin (2000) revised the species of Hemigrapha on Peltigerales but wrongly reported that Santesson lectotypified Hemigrapha on H. asteriscus in Hawksworth (1975) and this has been corrected by Ertz and Diederich (2015) by providing a new lectotype of Hemigrapha asteriscus. Diederich and Wedin (2000) included Hemigrapha in Microthyriaceae based on morphology. Eriksson et al. (2001) tentatively transferred Hemigrapha to Parmulariaceae. Inácio and Cannon (2008) revised Parmulariaceae but did not consider Hemigrapha in the family. Lumbsch and Huhndorf (2010), Hyde et al. (2013) and Wijayawardene et al. (2014) listed Hemigrapha in Parmulariaceae. Hyde et al. (2013) followed Eriksson et al. (2001) and included Hemigrapha in Parmulariaceae but mentioned that it is incertae sedis as molecular data was lacking. Hemigrapha resembles Viegasella in having star-shaped ascomata but can be differentiated in its smooth-walled ascospores while Viegasella has verrucose ascospores. Ertz and Diederich (2015) reported that Hemigrapha atlantica forms a sister lineage with the generic type H. asteriscus in their phylogenetic analysis based on mtSSU and nuLSU sequence data but no familial rank was provided. Dai et al. (2018) re-examined the syntype specimen of H. asteriscus under the code G 00292584 and reported that Hemigrapha in untypical with members of Parmulariaceae. In the phylogenetic analysis of Dai et al. (2018) based on LSU-SSU sequence data, Hemigrapha atlantica forms a single lineage within the order Asterinales and erected Hemigraphaceae to accommodate the genus. Hemigrapha is a distinct and type genus of Hemigraphaceae. Molecular markers available for Hemigrapha include mtSSU and nuLSU for H. atlantica.