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FOC | Family List | FOC Vol. 13 | Onagraceae

1. Ludwigia Linnaeus, Sp. Pl. 1: 118 ["Ludvigia"]; 2: [1204]. 1753.

丁香蓼属 ding xiang liao shu

Authors: Jiarui Chen, Peter C. Hoch & Peter H. Raven

Isnardia Linnaeus; Jussiaea Linnaeus; Oocarpon Micheli.

Herbs slender, erect to prostrate and rooting at nodes, or shrubs or rarely small trees; underwater parts often swollen and spongy or with inflated white spongy pneumatophores. Leaves alternate [or opposite], usually entire; stipules present, reduced and/or deciduous; bracteoles 2, at or near base of ovary, or absent. Flowers perfect, actinomorphic, in upper leaf axils or in spikes, racemes, or clusters; floral tube not prolonged beyond ovary. Sepals (3 or)4 or 5(-7), green, persistent after anthesis. Petals as many as sepals or absent, yellow or white, caducous. Stamens as many as or 2 × as many as sepals; anthers versatile or sometimes basifixed; pollen shed singly or in tetrads or polyads. Ovary with as many locules as sepals, rarely more, apex flat or conic, often with a depressed nectary surrounding base of each epipetalous stamen; stigma capitate or hemispheric, entire or lobed, upper 1/2-2/3 receptive. Fruit an obovoid to cylindric capsule, dehiscent irregularly or by a terminal pore or by flaps separating from valvelike apex. Seeds numerous, in one to several rows per locule, free or embedded in powdery or woody endocarp, raphe small or conspicuous, sometimes equal in size to body of seed. 2n = 16, 32, 48, 64, 80, 96, 128.

Eighty-two species: cosmopolitan, on all continents except Antarctica; nine species (one endemic) in China.

Ludwigia is distinctive within the family, and morphological, anatomical, and molecular evidence indicates that it is the sister group to the remainder of the family. Historically, plants of this affinity with stamen number equal to sepal number were Ludwigia, and those with stamens twice as many as sepals were Jussiaea, but Raven and others demonstrated reticulate variation in this character, and treated the two groups as a single genus. Polyploidy and autogamy are important evolutionary phenomena within the genus.

1 Sepals 5-12 mm; petals 6-18 mm   (2)
+ Sepals 1-4.5 mm; petals 1-3 mm or absent   (5)
2 (1) Sepals 4; stems densely villous-hairy or rarely puberulous; pedicels 1-10 mm; seeds free, with inflated raphe equal in size to body of seed; pollen in tetrads.   1 L. octovalvis
+ Sepals 5; stems subglabrous or rarely villous-hairy; pedicels 15-65 mm; seeds embedded in endocarp (sterile in L. ×taiwanensis), with inconspicuous raphe; pollen in monads   (3)
3 (2) Petals creamy-white with yellow base; plants with erect clusters of short, spindle-shaped pneumatophores at nodes of floating branches.   6 L. adscendens
+ Petals yellow throughout; plants often lacking pneumatophores at nodes of floating branches or when present mainly long and found on submerged stems   (4)
4 (3) Petals bright yellow; capsules fertile, 10-40 mm.   7 L. peploides subsp. stipulacea
+ Petals pale yellow; capsules sterile and abortive.   8 L. ×taiwanensis
5 (1) Plants prostrate or ascending, rooting at nodes; stems 20-45 cm; petals absent; capsules 3-5 mm, elongate-globose; seed raphe enlarged, triangular.   9 L. ovalis
+ Plants primarily erect, rooting only at stem base; stems 10-300 cm tall; petals present, yellow; capsules (3-)10-30 mm, cylindric or oblanceoloid; seed raphe inconspicuous   (6)
6 (5) Stamens 2 × as many as sepals; seeds in upper expanded capsule free, in 2+ rows per locule, 0.3-0.5 mm, seeds in lower capsule embedded in endocarp, in one row per locule, 0.7-0.9 mm.   5 L. hyssopifolia
+ Stamens as many as sepals, rarely more; seeds all free or all embedded throughout capsules, not mixed in arrangement or size   (7)
7 (6) Seeds 0.8-1.4 mm, embedded in endocarp; pollen in monads.   4 L. epilobioides
+ Seeds 0.3-0.6 mm, free, not embedded in endocarp; pollen in tetrads   (8)
8 (7) Sepals 4 or 5; capsules oblanceoloid, 2.5-5 mm thick, terete; seeds 0.3-0.5 mm; in 2+ rows or clusters per locule, not outlined through smooth capsule wall.   2 L. perennis
+ Sepals 4; capsules narrowly cylindric, 1-2 mm thick, somewhat 4-angled; seeds 0.5-0.6 mm; in 1 row per locule, clearly outlined through capsule wall.   3 L. prostrata

Lower Taxa


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