The genera of Lauraceae in Madagascar with nomenclatural novelties in Cryptocarya Author Werff, Henk van der Missouri Botanical Garden, P. O. Box 299, St. Louis, MO, 63166. henk.vanderwerff@mobot.org text Candollea 2017 2017-07-20 72 2 323 328 journal article 3482 10.15553/c2017v722a8 aab53827-c0c9-4ee3-b95c-f95f0e3919d1 2235-3658 5684462 Potameia Thouars Typus : Potameia thouarsii Roem. & Schult. Diagnostic characters. – The combination of dimerous flowers (flowers with 4 tepals and 6 or fewer stamens) and alternate leaves. Distribution. – Endemic to Madagascar (but see notes). Number of species . – Estimated at 25 (all endemic) Recent literature. – VAN DER WERFF (1991 , 1996 ). Notes . – Potameia is closely related to Beilschmiedia and differs from that genus by its dimerous flowers. Both genera have fruits seated on the pedicel with remnants of the tepals at the base, four in Potameia and six in Beilschmiedia . One species of Beilschmiedia ( B. pedicellata van der Werff ) may have dimerous flowers, but differs from Potameia in its opposite leaves (all species of Potameia have alternate leaves). Most species of Potameia have flowers with six bilocular stamens. In a few species the adjacent locelli become fused so the stamens are unilocular. The number of stamens can also be reduced; the extreme is P. micrantha van der Werff , a species with flowers with two stamens, each unilocular. Most herbarium specimens of Potameia have a light colored, grey bark. While such a bark color may also occur outside Potameia , its presence strongly suggests Potameia . Several Asian species, mostly from southern China , have been placed in Potameia but are now considered to belong to Syndiclis Hook. f.. The single Indian species placed in Potameia , P. tirunelvelica (Manickam, Murugan, Jothi & Sundaresan) M. Gangop. , was originally placed in Beilschmiedia ; the description stated that it has opposite leaves and dimerous flowers. Because the combination of opposite leaves and dimerous flowers also occurs in a Beilschmiedia and not in Potameia , I consider the Indian species as a Beilschmiedia and Potameia as a genus endemic to Madagascar . Potameia is in need of taxonomic revision.