Minute, mostly glabrous, aquatic or mud-loving succulent herbs, with opposite entire leaves and very small solitary axillary flowers. Calyx 3-5-parted. Petals 3-5, distinct, or united at the base. Stamens 3-5. Carpels 3-5, distinct. Styles short. Ovules usually few. Follicles few-seeded or several-seeded. [Latin, from the affinity of these plants with the genus Tillaea.]

About 20 species, of wide geographic distribution. Besides the following, another occurs in the western and southern States

1. Tillaeastrum Aquáticum (L.) Britton. Pigmy-Weed

Fig. 2131

Tillaea aquatica L. Sp. Pl. 128. 1753.

Tillaea simplex Nutt. Journ. Acad. Phil. 1: 114. 1817.

Bulliarda aquatica DC. Prodr. 3: 382. 1828.

Tillaeastrum aquaticum Britton, Bull. N. Y. Bot. Gard. 3: 1. 1903.

Stems ascending or erect, 1/2'-3' high, glabrous. Leaves linear-oblong, entire, acutish or obtuse at the apex, connate at the base, 2"-3" long, at length shorter than the internodes; flowers sessile or short-peduncled, 1/2" broad; calyx-lobes,petals, stamens and carpels 4, rarely 3, petals greenish, about twice the length of the calyx-lobes; follicles ovoid, longer than the calyx-lobes, 8-10-seeded.

Muddy banks of streams, Nova Scotia to Massachusetts and Maryland, Louisiana and Texas, near the coast, Washington to Lower California and Colorado. Stem often rooting at the nodes. Also in Europe and northern Africa. July-Sept.

2. Tillaeastrum Vaillántii (Willd.) Britton. Vaillant's Pigmy-Weed

Fig. 2132

Tillaea Vaillantii Willd. Sp. Pl. 1: 720. 1798.

Tillaeastrum Vaillantii Britton, Bull. N. Y. Bot. Gard. 3: 2. 1903.

Similar to the preceding species, 4' long or less, the oblong to linear-oblong leaves about 2" long. Fruiting peduncles elongated, .becoming as long as the leaves or longer.

Prince Edward Island; Nantucket. Europe and northern Africa. Perhaps a race of the preceding species.