The genus Pausandra Radlk.

The genus Pausandra Radlk. belongs to the Tribe Cluytieae of the Euphorbiaceae. It was described by Radlkofer in 1870 in Flora LIII pp. 79—95. The genus is based on Thouinia Morisiana of Casaretto. In his paper Radlkofer discussed at length that this species does not belong to the Sapindaceous genus Thouinia, but represents a new genus of the Euphorbiaceae. As at that time female flowers were unknown Radlkofer stated that the systematic position of the new genus was still doubtful, but that most probably it should belong to a new subtribe of the Jatropheae. Two new species were described in the genus in 1873 by Baillon, P. Trianae Baill. based on Pogonophora Trianae Müll. Arg. which was published in 1864, and P. Martinii Baill. based on very young material and erroneously described by Baillon as being 3-merous, as will be discussed below. He placed the genus in the affinity of Argithamnia Sw., which is certainly not right as this genus is quite different both in habit and in flowercharacters. A fourth species was added by Müller Arg. in 1874 in Flora Brasiliensis XI. II., where he inserted the genus in the same group as was suggested by Radlkofer. No more species had been described when Pax published in 1911 his monograph of the Tribe Cluytieae Pax in Engler, Das Pflanzenreich IV. 147. III. He inserted the genus Pausandra Radlk, with the genera Givotia Griff, and Ricinodendron Müll. Arg. in a new subtribe Ricinodendrinae Pax. I think that this is the right position for the genus, though it could be placed in a separate subtribe for its penninerved, glanduliferous leaves and the capsular fruits. It was a pity that Pax published this monograph without studying the original material. He now copied Baillon’s bad descriptions and the lack of a thorough study on the genus caused the publication of several superfluous species in recent years. P. quadriglandulosa Pax et K. Hoffm. and P. extorris Standley described in 1919 and 1929 are the same as P. Trianae (Müll. Arg.) Baill. P. flagellorhachis Lanj. is identic with P. Martinii Baill., while it was proved that the latter species is not trimerous. P. integrifolia Lanj. could not be maintained in the genus. Only the two new species published by Ducke in 1925 were truly new ones. Moreover three new species were recognized in the recent collections made by Krukoff in Brazil. It is for all these reasons that it seemed to me highly desirable to give a new treatment of this genus. Perhaps several of the old and new species can be united, as one can find often only small differences, but for the present I think it advisable to keep them separate. Pausandra Radlk, has been described to be dioecious, but recently it has been proved in some species that they are monoecious, so it is probable that most of them are under special cicumstances.