Two adventitious species of the genus Beckmannia Host have been found in the Netherlands. They can be distinguished as follows: 1. Stems mostly tuberously thickened at the base. Spikelets always 2-flowered (fig. 1, a). Glumes always more or less irregularly dentate at the mostly rounded and mostly very shortly acuminate apex, and with often very shortly ciliate margins, hardly swollen when ripe. Ripe stamens mostly distinctly exserted; anthers 1,6—2,1 mm long (fig. 1, b) B. eruciformis (L.) Host 1’. Stems not thickened at the base. Spikelets 1-flowered (fig. 1, c); sometimes a few 2-flowered spikelets are present in the spike. Glumes entire at the acute and distinctly acuminate apex, and with glabrous margins, mostly rather strongly swollen when ripe. Ripe stamens mostly but slightly exserted; anthers 0,7—1,1 mm long (fig. 1, d) ... B. syzigachne (Steud.) Fern.