Three new adventitious species of Amaranthaceae are recorded for the Netherlands: Gomphrena celosioides Mart., Alternanthera ficoidea (L.) R. Br. ex Grisebach var. bettzickiana (Regel) Backer and an unidentified species of Alternanthera. Of the latter a description is given and the identification is requested. Gomphrena and Alternanthera can be separated as follows: 1. Stigma capitate or shortly ................... 2-lobed Alternanthera 1’. Stigma branches 2, filiform to subulate ................... Gomphrena Gomphrena globosa and G. celosioides are easily recognized by the dorsal crest of the bracteoles. The species of Alternanthera here described can be fitted in the key given by VAN OOSTSTROOM & REICHGELT (1961) in the following manner: 0. Anthers lanceolate to linear; pseudostaminodes ligular with laciniate apex. 00. Bracts and bracteoles ca. ¾ times as long as the tepals. Outer tepals with 3—5 thick nerves at base. Pseudostaminodia ± as long as the stamens. A. ficoidea var. bettzickiana 00’. Bracts and bracteoles longer than the tepals. Outer tepals at most faintly nerved. Pseudostaminodia shorter than the stamens .................. A. spec. 0’. Anthers ellipsoid; pseudostaminodia narrowly triangular to linear-subulate, entire. 1. Tepals etc.