63. Polygonum polygamum Vent., Descr. Pl. Nouv.: tab. 65. 1802.

Lectotypus (designated here): [UNITED STATES]: Hort. Cels, Ventenat s.n. (G [G00341643 specimen on the left]!) (Fig. 11).

Notes. – The only collection of this species in Ventenat’s herbarium is mixed: a Ventenat collection from Cels’s garden and fragments of possible isotypes (G [G00341643 specimen on the right]) of Polygonella parvifolia Michx., a name published one year later (Michaux, 1803) (with a duplicate in P-JU n° 4290 [P00681748]). The latter name is probably based on the same original material as mentioned on the sheet by Vernon M. Bates (Fig. 11) but we failed to find convincing type material in P-MICH due to the complicated taxonomy of the mixed collections and leave this to a specialist of this genus. Horton (1963: 198) designated tab. 65 of Descriptions in 1802 as the lectotype for the name Polygonum polygamum but as original material has been found, our lectotypification supersedes the previous one. We designate Ventenat’s collection as the lectotype (specimen on the left of the sheet marked with an asterix). Recent molecular phylogenetic data show that Polygonella Michx. is embedded in Polygonum L. and Polygonella is currently recognised at the subsectional level within Polygonum (Schuster et al., 2011) .