Mycoheterotrophic Plants

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Thismia petasiformis D.F. Silva & J.M.A. Braga

Thismia petasiformis is described in Ferreira da Silva & Alvarenga Brava (2022), collected in northwestern Mato Grosso/Brazil, from a remaining forest patch in the brasilian Amazon forest. Due to the strong deforestation activity in this region, this species is critically endangered. T. petasiformis is closest to T. fungiformis and T. melanomitra, all of them having horizonal vermiform roots, pyramidal stigmata, non-sculptured connectives and parietal placentation. However, T. petasiformis differs from T. fungiformis by having a roughly trigonous corolla tube, upwardly arched outher perianth lobes and a mitre built up by fusing the inner perianth lobes, whereas T. fungiformis has a terete corolly tube, reflexed outer perianth lobes and inner perianth lobes not united but being peltate and having a bowl-shaped structure at the flattened apex. T. melanomitra shares the fused inner perianth lobes with T. petasiformis, but has six bowl-shaped depressions (foveae) at its apex (Maas & Maas 1987), which are absent in T. petasiformis. Moreover, T. petasiformis has smaller flowers being brownisch in contrast to the lead-grey mitre of T. melanomitra and its annulus is inconspicuous (prominent in T. melanomitra).

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith