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FOC | Family List | FOC Vol. 13 | Lythraceae

8. Rotala Linnaeus, Mant. Pl. 2: 143, 175. 1771.

节节菜属 jie jie cai shu

Authors: Haining Qin & Shirley A. Graham

Herbs, annual or perennial, aquatic, amphibious, or terrestrial, often anthocyanic with age. Stems glabrous, simple or branched, commonly 4-angled or 4-winged. Leaves decussate or whorled, sessile or subsessile; bracts of inflorescences like foliage leaves or smaller and different in shape. Flowers actinomorphic, monomorphic [or dimorphic], (3 or)4(-6)-merous, solitary, sessile or shortly pedicellate, in axils of bracts on main stem, on spikelike lateral branchlets, or in terminal spikes. Floral tube campanulate or urceolate, generally globose in fruit; bracteoles 2, at base of floral tube; sepals 3-6, ca. 1/3 length of floral tube or less, deltate; epicalyx alternating with sepals or absent. Petals 3-6, pink-purple to whitish. Stamens 1-6, opposite the sepals. Ovary 2-4-loculed; style long or short; stigma capitate, rarely more massive, discoid. Capsule finely transversely striate (10 × magnification), hyaline, septicidally dehiscent, 2-4-valved. Seeds numerous, brown or reddish brown, ovoid to ellipsoidal, concave-convex, less than 1 mm.

About 46 species: tropical and temperate regions of the world; ten species (one endemic, one naturalized) in China.

An additional species, Rotala hippuris Makino (Bot. Mag. (Tokyo) 12: 81. 1898), a popular aquarium plant considered endemic to Japan, is found in ornamental ponds in Taiwan. It was reported (Liu et al., Man. Taiwan Vasc. Pl. 3: 241. 2000) from ponds at Taoyuan, Taiwan. Whether it is native, naturalized, or cultivated there was not stated.

See also Cook, A revision of the genus Rotala (Lythraceae) (Boissiera 29: 1-156. 1979).

1 Leaves whorled   (2)
+ Leaves decussate   (3)
2 (1) Flowers in terminal racemes, pedicellate; petals present; stamens 4; aerial leaves 3-12-whorled, submerged leaves more numerous.   1 R. wallichii
+ Flowers solitary, axillary, sessile; petals absent; stamens (1 or)2 or 3(or 4); aerial and submerged leaves 3-5[-8]-whorled.   2 R. mexicana
3 (1) Stipulelike outgrowths present at nodes; sepals 6.   3 R. hexandra
+ Stipulelike outgrowths absent at nodes; sepals 3-5   (4)
4 (3) Flowers in 1 or more densely flowered terminal spikes; stigma massive, discoid; foliage leaves obovate-elliptic to orbicular or elliptic.   4 R. rotundifolia
+ Flowers in axillary spikes (lateral branchlets) or sessile in bracts on main stem; stigma capitate to punctiform; foliage leaves various   (5)
5 (4) Leaf margin translucent to opaque white cartilaginous; capsules 2-valved.   5 R. indica
+ Leaf margin green, membranous; capsules 3- or 4-valved   (6)
6 (5) Stems broadly 4-winged, wings running to or onto leaves; bracts of inflorescence distinctly smaller than foliage leaves; flowers in axillary spikes or less often sessile on main stem   (7)
+ Stems terete or 4-angled, not distinctly winged; bracts of inflorescence like foliage leaves; flowers sessile on main stem   (8)
7 (6) Stem wings running onto the leaves; flowers in axillary spikes; sepals 4; epicalyx segments between sepals absent.   6 R. cordata
+ Stem wings running to the leaves; flowers in axillary spikes or sessile on main stem; sepals 5; epicalyx segments between sepals setiform, ca. 1/2 as long as floral tube or longer.   7 R. densiflora
8 (6) Stamens 5; capsule 3-valved, well exserted from floral tube, red at apex.   8 R. rosea
+ Stamens 4; capsule 4-valved, included in or slightly exserted from floral tube, golden brown   (9)
9 (8) Leaves oblanceolate, narrowly oblanceolate, or elliptic, apex obtuse; capsule slightly exserted from floral tube.   9 R. ramosior
+ Leaves obovate-oblong, apex acute or subacute; capsule included in floral tube.   10 R. taiwaniana

Lower Taxa


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