Developmental Morphology of the “Zwischengruppe” between Ascohymeniales and Ascoloculares

  • A. Henssen
  • G. Thor
Part of the NATO ASI Series book series (NSSA, volume 269)


Characteristic features of the “Zwischengruppe”, the Arthoniales s.l., are the ascohymenial ascocarp ontogeny and fissitunicate asci. The asci have a thick exotunica and a thin, expanding, hemiamyloid endotunica with an apical amyloid structure. The ascocarps are apothecioid, lirelliform, or in some genera stromatic. They develop gradually from a generative tissue that includes ± bent ascogonia ending in a trichogyne. The hamathecium consists of paraphysoids, and the exciple is annular and rudimentary to cupular and carbonized. The ascocarp ontogeny is briefly discussed in the type species of Arthonia, Arthothelium, Opegrapha, and Roccellina, and more comprehensively in species of Melampylidium, Dichosporidium, and Erythrodecton. The developmental morphology of the “Zwischengruppe” is compared with that of Pleospora herbarum and Myriangium duriaei, members of the Ascoloculares s.str. with ± pseudoparenchymatous ascostromata. Diagnoses are provided for the new species Dichosporidium latisporum Thor & Henssen and Melampylidium redonii Henssen. The new combination Melampylidium macrosporum (R.C. Harris) Henssen is made.


Generative Tissue Developmental Morphology Ascogenous Hypha Opus Botanica Young Ascus 
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Copyright information

© Springer Science+Business Media New York 1994

Authors and Affiliations

  • A. Henssen
    • 1
  • G. Thor
    • 2
  1. 1.Fachbereich BiologiePhilipps-UniversitätMarburgGermany
  2. 2.Institutionen för ekologi och miljövårdSveriges LantbruksuniversitetUppsalaSweden

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