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Flora of Taiwan | Family List | Onagraceae

Ludwigia L.

水丁香屬

RAVEN, PETER H. and PENG, CHING-I

Ludwigia epilobioides

Credit: HAST

Herbs, shrubs, or small trees, mostly of wet places, sometimes floating in open water. Leaves alternate (in Taiwan) or opposite, rarely whorled; stipules present, caducous. Flowers (3-)4-5(-7)- merous, in axils of reduced leaves. Floral tube absent, the sepals persistent after anthesis, sepals (3-)4-5(-7); petals as many as the sepals or absent, yellow or in a few species white, not deeply notched. Stamens as many as or twice as many as the sepals; pollen shed singly or in tetrads. Ovary with as many locules as the sepals, the seeds numerous in each locule. Capsules dehiscent or indehiscent.

About 80 species, pantropical but mostly in the New World, and well represented in temperate regions also. Six species and one hybrid occur in Taiwan.

Gu, H. Y., C. J. Chen, C. Q. Liu, L. J. Qu & N. S. Pan 1991. On distribution, cytology, and systematics of Ludwigia Sect. Oligospermum in China. Cathaya 3: 37-44. Peng, C. I. 1983. Triplodidy in Ludwigia in Taiwan, and the discovery of Ludwigia adscendens (Onagraceae). Bot. Bull. Acad. Sin. 24: 129-134. Peng, C. I. 1990. Ludwigia x taiwanensis (Onagraceae), a new species from Taiwan, and its origin. Bot. Bull. Acad. Sin. 31: 343-349. Raven, P. H. 1963. The Old World species of Ludwigia (including Jussiaea), with a synopsis of the genus (Onagraceae). Reinwardtia 6: 627-347.


KEY TO SPECIES

1 Plant prostrate or ascending, rooting freely at nodes.   (2)
+ Plant erect, rooting only at stem base.   (4)
       
2 (1) Leaves (0.4-) 1-7.5 (-9.5) cm long, narrowly elliptic to spatulate-oblong; sepals 6-12 mm long; petals 5; stamens 10.   (3)
+ Leaves 0.5-2.5 cm long, ovate to elliptic ovate; sepals 1-3 mm long; petals 0; stamens 4.   Ludwigia ovalis
       
3 (2) Petals creamy white with a yellow base; pollen fertile; ovaries mature into capsules.   Ludwigia adscendens
+ Petals creamy white with a yellow base; pollen fertile; ovaries mature into capsules.   Ludwigia x taiwanensis
       
4 (1) Sepals 6-15 mm long; petals 5-17 mm long; seeds free, with an enlarged raphe about equal in size to the seed body.   Ludwigia octovalvis
+ Sepals 1.5-4.5 mm long; petals 1-3 mm long; seeds free or embedded in a chunk of endocarp at maturity, without enlarged raphe.   (5)
       
5 (4) Stamens twice as many as the sepals; seeds free and multiseriate in upper locules of the capsule, embedded in chunk of endocarp and uniseriate in lower locules of the capsule   Ludwigia hyssopifolia
+ Stamens as many as the sepals; seeds otherwise.   (6)
       
6 (5) Capsules oblanceolate; seeds 0.3-0.5 mm long, all free, in clusters in each locule.   Ludwigia perennis
+ Capsules linear or narrowly elliptic-lanceolate; seeds 0.7-1 mm long, all embedded in endocarp, in 1 (or 2) row(s) in each locule.   Ludwigia epilobioides

Lower Taxa

Related Synonym(s):


 

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