21. Myosoton Moench, Methodus. 225. 1794.
Giant or water chickweed, stellaire aquatique [Greek myos, mouse, and otos, ear, alluding to leaves]
Richard K. Rabeler
Herbs, perennial. Taproots slender, rhizomes slender. Stems decumbent to ascending, simple or branched, terete to angular. Leaves sessile leaves clasping proximally, petiolate (proximal leaves) or sessile (most cauline leaves); blade 1-veined, ovate to broadly elliptic, not succulent, apex acute. Inflorescences axillary or terminal, open cymes; bracts paired, foliaceous, smaller. Pedicels ascending to erect, reflexed in fruit. Flowers bisexual, occasionally pistillate or reduced and sterile; perianth and androecium weakly perigynous; hypanthium minimal; sepals 5, distinct, green, ovate, 4-6(-9) mm, herbaceous, margins green or white, herbaceous or scarious, apex acute, not hooded; petals 5, white, claw absent, blade apex deeply 2-fid; nectaries at base of filaments opposite sepals; stamens 10, occasionally fewer, arising from nectariferous disc at ovary base; filaments distinct; staminodes sometimes present, linear; styles 5(-6), distinct, filiform, 0.7-1.8 mm, glabrous proximally; stigmas 5(-6), linear along adaxial surface of styles, papillate (30×). Capsules ovoid to globose-ovoid, opening by 5(-6), slightly recurved, briefly 2-fid valves; carpophore absent. Seeds 50-100, brown-blackish, reniform, laterally compressed, papillate, marginal wing absent, appendage absent. x = 14.
Species 1: introduced; Europe, temperate Asia.
The combination of 5(-6) styles and a capsule opening by the same number of briefly 2-fid valves characterizes Myosoton and is not known in Stellaria. Most chromosome counts of M. aquaticum are 2n = 28, a very rare number in Stellaria.