Description and taxonomic position of Maclura brasiliensis (Moraceae)

During study of American Chlorophotas (Kaastra 1972) Chlorophora brasiliensis (Martius) Standley (= Maclura brasiliensis (Martius) Endlicher) and Chlorophora scandens Standley et Williams seemed not to be closely related to Chlorophora tinctoria (L.) Bentham et Hooker. The taxonomic position of Maclura brasiliensis was already called dubious by Bentham & Hooker (1880) and more recently also by Macbride (1937); the same holds true for Chlorophora scandens (Standley & Williams 1950). Chlorophora brasiliensis and Chl. scandens show much resemblance to some other genera treated by Corner (1962) as sections of Maclura: Maclura Nuttall s.s. (= Maclura pomifera (Rafinesque) Schneider), Cardiogyne Bureau, and Cudrania Trécul. Corner, however, did not mention Chlorophora brasiliensis nor Chl. scandens. There is at least one other taxon that seems to be closely related to the group concerned here, the genus Plecospermum Trecul. Bentham & Hooker (1880) combined Plecospermum with Cardiogyne; Corner (l.c.) regarded it as a distinct but problematic genus. Richter (1895), on account of anatomical studies, pointed out that Plecospermum, Cardiogyne, and Cudrania could be regarded as a single genus.