Hydrocotyle verticillata Thunb. var. triradiata (A. Rich.) Fern., whorled marsh pennywort, whorled waterpenny. Perennial herb, rhizomatous, fibrous–rooted at nodes, lacking aboveground stems, with ascending leaves and flowering shoots, in range to 20 cm tall; shoots with only cauline leaves, glabrous, lacking any distinctive odor; rhizomes cylindric, 1.2—1.5 mm diameter, white, internodes often 20—60 mm long, with tuberlike swelling at node; adventitious roots at nodes.

Leaves

Leaves alternate, simple and umbrellalike (peltate), long–petiolate, with stipules; stipules 2, attached to stem, broadly triangular, < 2 mm long, scarious and brownish or with purplish spots; petiole cylindric, 35—200+ mm long, white belowground and green aboveground; blade round to broadly kidney–shaped, 21—35 × 24—40 mm, slightly wider than long, with 8—11(—13) shallow, subequal lobes, cordate at base, crenate on lobe margins, palmately veined to each lobe, glossy.

Inflorescence

Inflorescence interrupted “spike” of whorled flowers at nodes (verticils), axillary, with axis unbranched, verticals to 5, each verticil 4—8(—15)–flowered (appearing greater at tips because rachis not elongated), bracteate, glabrous; peduncle 25—175 mm long, mostly < petiole; rachis internodes between lower verticils 5—30 mm long; bractlet subtending pedicel boat–shaped, 1.2—1.6 mm long, narrowly membranous on margin; pedicel at anthesis 3—5 mm long increasing slightly in fruit.

Flower

Flower bisexual, radial, 2—2.8 mm across; sepals absent; petals 5(—6), ascending to spreading at anthesis (corolla star–shaped), triangular–ovate, 0.5—1.3 × 0.4—0.8 mm,white, often persistent during some fruit development; stamens 5, free, alternate with petals; filaments spreading to ascending, ± 0.7 mm long, greenish white; anthers versatile, dithecal, ca. 0.3 mm long and wide, yellowish green aging orangey yellow, longitudinally dehiscent; pollen yellowish; pistil 1; ovary inferior with ± fleshy, green cushionlike platform (stylopodium, stylar tissue) on top, roundish and compressed ⊥ septum, ca. 1.2 mm wide, 2–chambered, each chamber with 1 ovule; styles 2, at anthesis ca. 0.3 mm long increasing in fruit, pale green; stigmas terminal, minute, green aging reddish.

Fruit

Fruit schizocarp, of 2 dry 1–seeded halves (mericarps), mericarps hemispheric compressed side–to–side, 1.8—2 × 1.1—1.5 mm,ca. 0.7 mm thick on margin with fruit wall unevenly thickened around seed, weakly ribbed, glabrous; carpophore absent.

Seed

SeedD–shapedandcompressed side–to–side,ca. 1.2 mm long, firmly attached to fruit wall.

A. C. Gibson