Aquatic or marsh herbs. Leaves linear or lanceolate. Flowers in umbel-like cymes, regular, hermaphrodite. Perianth of 6 segments, all, or the inner ones only, petal-like. Stamens 9, very rarely fewer. Pollen-grains globular. Carpels 6, very rarely fewer, distinct or united at the base only, opening when ripe along the ventral suture. Ovules on irregularly branched parietal placentas, numerous, inverted. Seeds without albumen.—Genera 2, species 2. North and Central Africa. (Under ALISMACEAE.)
Perianth-segments nearly equal, all petal-like, pink, persistent. Embryo straight. Leaves linear. Juice not milky.—Species 1. North-west
Africa (Algeria). Used as a garden plant. The root-stock is edible.
“Flowering-rush.” Butomus Tourn.
Perianth-segments unequal, outer sepal-like, inner petal-like, white, falling off very early. Embryo horseshoe-shaped. Leaves elliptical. Juice milky.—Species 1. Northern part of Central Africa. (Butomopsis
Kunth) Tenagocharis Hochst.
[FAMILY 14.] HYDROCHARITACEAE
Aquatic herbs. Leaves with axillary scales. Flowers enclosed when young in a one-or several-flowered spathe of one or two bracts, regular, rarely somewhat irregular. Perianth consisting of a calyx and a corolla, rarely simple. Stamens 2-12. Anthers opening outwards or laterally. Ovary inferior, more or less distinctly one-celled, with 2-15 parietal placentas, which sometimes form incomplete dissepiments. Seeds without albumen.—Genera 10, species 40. (Plate 7.)
1. Stigmas 2-5. Placentas as many, slightly raised. 2
Stigmas 6 or more. Placentas as many, much projecting and generally meeting in the centre of the ovary. 6
2. Petals none. Stamens 3. Pollen-grains filiform. Stigmas several times as long as the sepals. Embryo with a strongly developed radicle.
Totally submerged marine plants. Leaves more or less distinctly stalked.—Species 2. Indian Ocean. [Subfamily HALOPHILOIDEAE.] Halophila Thouars
Petals present, but sometimes very small and falling off very early. Pollen-grains globular. Stigmas at most twice as long as the sepals. Embryo with a not very strongly developed radicle. Freshwater plants; flowers raised above the water. Leaves sessile. [Subfamily VALLISNERIOIDEAE.] 3
3. Leaves whorled. Spathes 1-flowered. Flowers unisexual. Stamens 3.—Species
1. Upper Nile, Madagascar, Mauritius. Used in refining sugar. [Tribe HYDRILLEAE.] Hydrilla L. C. Rich.
Leaves spirally arranged. Spathes of the male flowers several-flowered. 4
4. Spathes of the male flowers 2-10-flowered, not breaking away from the stem. Stamens 3-9. Ovules inverted.—Species 3. Madagascar and
Angola. [Tribe BLYXEAE.] Blyxa Noronha
Spathes of the male flowers many-flowered, breaking away from the stem.
Stamens 2-3. Ovules straight. [Tribe VALLISNERIEAE.] 5
5. Male flowers regular, with 3 fertile and 2-4 sterile stamens. Stigmas linear, 2-cleft or 2-parted. Leaves one-nerved. Stem elongated.—Species
10. Tropical and South Africa. Lagarosiphon Harv.
Male flowers somewhat irregular, with 2-3 fertile stamens and sometimes
a sterile one. Stigmas ovate, notched or two-toothed. Leaves several-nerved.—Species
2. North and Central Africa. Used in refining sugar. Vallisneria Mich.
6. Leaves in two rows. Ovules inverted, inserted in the angles formed by the placentas and the wall of the ovary. Radicle of the embryo strongly developed. Marine plants. [Subfamily THALASSIOIDEAE.] 7
Leaves in rosettes. Ovules inverted, but inserted on the whole surface of the placentas, or straight. Radicle of the embryo not strongly developed. Freshwater plants. [Subfamily STRATIOTOIDEAE.] 8
7. Scape of the male flowers short, of the female long and at length spirally twisted. Male spathes several-flowered; flowers with 3 petals and 3 stamens.—Species 1. Madagascar and Red Sea. Yields fibres and edible seeds. Enalus L. C. Rich.
Scapes moderately long, not spirally twisted. Male spathes one-flowered; flowers without petals, with 6 stamens.—Species 1. East Africa. Thalassia Soland.
8. Placentas undivided. Ovules straight. Fertile stamens 9. Stem emitting runners. Leaves floating.—Species 1. Algeria and Madagascar.
“Frogbit.” [Tribe HYDROCHARITEAE.] Hydrocharis L.
Placentas two-cleft. Ovules inverted. Seeds very numerous. Fertile stamens 6-12. Stem very short, without runners. Leaves at least partially submerged. [Tribe OTTELIEAE.] 9
9. Flowers hermaphrodite. Spathes one-flowered. Stigmas 6.—Species 9.
Tropics and Egypt. Some are used as vegetables. (Plate 7.) Ottelia Pers.
Flowers dioecious. Spathes of the male flowers several-flowered. Stigmas
9-15.—Species 10. Tropics. Some are used as vegetables. Boottia Wall.
ORDER TRIURIDALES
[FAMILY 15.] TRIURIDACEAE
Small, pale, yellowish or reddish herbs. Leaves reduced to scales. Flowers in racemes, regular, monoecious. Perianth of 6 petaloid, valvate segments united at the base. Stamens 3; filaments short or wanting; anthers 2-celled, opening transversely. Carpels inserted on a convex or conical receptacle,
HYDROCHARITACEAE.