BOTANY WITH THE BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

X. SEED PLANTS

Family Waterworts (Elatinaceae)

Annual aquatic and semi-aquatic plants with delicate, transparent, densely leafy stems that often ROOT at the nodes. These plants are entirely submerged in Water. Phyllotaxy is opposite or whorled. Leaves are simple or coarsely toothed. Flowers are small, bisexual, solitary or clustered in the leaf axils. The perianth is double, with four sepals and petals, and eight stamens. The fruit is a capsule. Floral formula: *K₄C₄A₈G_(4). There are two genera and 40 species, distributed mainly in the tropical and subtropical regions of both hemispheres. In Ukraine, the family is represented by 4 species of a single genus — waterwort (Elatine).

Eight-stamened waterwort (Elatine alsinastrum L.). An annual plant, 5-35 cm tall; thenagophyte, hydrochthophyte, hydrophil, anemophil, hydrochore, ornithochore. Stem hollow, erect or ascending, weak, transparent, densely leafy, branched at the base, often rooting at the lower nodes. Phyllotaxy is whorled. Leaves sessile, entire, with small stipules, dimorphic. Submerged leaves are narrowly linear, single-veined, 8-12 per whorl; emergent leaves are oblong-obovate or oval, three-veined, 3-6 per whorl.

Flowers regular, small, bisexual, sessile, axillary, solitary or clustered in the leaf axils. Perianth double, sepals 1-2 mm long, petals white, 1.5-2.5 mm long. Gynoecium syncarpous, Ovary four-locular. Styles with capitate stigmas. Fruit is a capsule with numerous seeds up to 0.1 mm long. Blooms underwater or above the water surface in May–(June)–August. Propagated by seeds.

Grows in shallow standing water bodies, floodplains, and swamps, scattered throughout Ukraine except for the Crimea. Two aquatic forms and one terrestrial form are known. Aquatic forms: f. aquatica Seub. — with branched stems, leaves longer than the internodes, and flowers in whorls of three; f. fluitans Seub. — with unbranched, weak stems, floating leaves shorter than the internodes, and flowers in solitary racemes. Terrestrial form: f. terrestris Seub. — with nearly simple, low stems, 2-10 cm long.

Asian waterwort (Elatine ambigua Wight). An annual plant, 1.5-3 cm tall, with branched, creeping or ascending stems. Leaves opposite, petiolate. The number of stamens equals the number of petals. Calyx trifid, its lobes two to three times shorter than the petals and capsules. Pedicels 1.5-2.5 mm long, equal to or twice as long as the petals. Seeds nearly straight or slightly curved. Blooms in July-August.

Grows on the banks of water bodies and along ditches in Transcarpathia (vicinity of Uzhhorod and Berehove).

Hungarian waterwort (Elatine hungarica Moesz). An annual plant, 2-6 cm tall. Stems branched, phyllotaxy opposite. Leaves oblong-lanceolate or oblong-ovate, obtuse, mostly petiolate. Flower pedicellate. Corolla shorter than the calyx. Blooms in June-August.

Grows on the banks of water bodies, in ditches, and in water. Rarely found in the Steppe zone (in the south) and Transcarpathia.

Water-pepper waterwort or curved-seed waterwort (Elatine hydropiper L., E. gyrosperma Duebenj.). An annual plant, 2-10 cm tall; thenagophyte, hydrochthophyte, anemophil, hydrophil, hydrochore, ornithochore. Stems slender, branched, creeping or ascending, rooting at the nodes. Phyllotaxy opposite. Leaves short-petiolate, oblong-ovate, 0.5-1 cm long.

Flowers nearly sessile, bisexual, axillary. Perianth double. Calyx 0.7 mm long, four-parted, with broadly lanceolate lobes. Corolla white or pink, longer than the calyx. Fruit is a depressed-globose capsule, up to 2 mm in diameter. Seeds curved, horseshoe-shaped, up to 0.3 mm long. Blooms underwater or above the water surface in May–(June)–September. Propagated by seeds.

Grows in standing water bodies, muddy swamps, in water, and along shores throughout Ukraine except for the Crimea.

Terrestrial and shallow-water forms are known. Terrestrial form: f. terrestris Seub. — with a highly branched, tiny stem up to 2 cm tall, short-petiolate leaves clustered into a rosette at the branch tips, and pink corollas. Shallow-water form: f. intermedia Seub. — a larger plant with transparent leaves whose petioles equal the blade, and white corollas; f. submersa Seub. — a plant of flowing waters with an elongated, sparsely branched stem and few flowers with a white corolla.