Taxon: Hydrogonium arcuatum

Plate 123. 1–4, Hydrogonium anceps. 1, leaf (× 45). 2, apical leaf cells (× 325). 3, basal leaf cells (× 325). 4, cross section of leaf (× 325). 5–9, Hydrogonium arcuatum. 5, habit (× 3). 6, 7, leaves (× 45). 8, apical leaf cells (× 325). 9, capsule (× 20).