Ludwigia hyssopifolia

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Ludwigia hyssopifolia


Annual herb 5 cm to 3 m, often becoming woody at the base; Leaves lanceolate, 1-9 by 0.2-3 cm, narrowly cuneate at the base, apex acuminate; Sepals 4, lanceolate, 2-4 by 0.7-1.2 mm, finely puberulent, 3-nerved. Petals yellow, fading orange-yellow, elliptic, 2-3 by 1-2 mm. Stamens 8, pale greenish yellow, epipetalous ones shorter; Capsule relatively thin-walled, finely puberulent, 1.5-3 cm by 1-1.2 mm, subterete, enlarged in the upper 1/6 to ⅓, subsessile. Lower part of capsule at first marked by distinct bumps corresponding to the position of the uniseriate seeds, but as the endocarp hardens and swells, the capsule becomes smooth. Seeds in upper inflated portion of the capsule multiseriate, free, ovoid, 0.35-0.5 mm long, paler brown than the lower seeds and with a narrower raphe.


Africa: Gulf of Guinea Is. (São Tomé present), Arnhem Land present, Asia-Temperate: Hainan (Hainan present), Asia-Tropical, Cape York Peninsula present, Ceylon present, Continental SE. Asia present, Dakar to Lake Chad, S. Sudan and S. Congo present, Micronesia present, N. Australia present, Tropical Africa present present
Tropical Africa (Dakar to Lake Chad, S. Sudan and S. Congo), continental SE. Asia (Ceylon to Hainan), throughout Malesia to Micronesia and N. Australia (Cape York Peninsula and Arnhem Land).
It is difficult to fix the native country of this now widely spread palaeotropical weed which has no close relatives. It might have been introduced in tropical Africa where it is relatively local and confined to the west, but it was collected in Sao Tome as early as 1822.


BACKER () described in detail the biology of this species, of which the flowers open at 7 a.m. Seeds are gradually released by decay of the pericarp of which the vessels remain persistent. To his surprise both kinds of seed were buoyant for 16 days, after which they sank. On the 17th day he observed one buoyant seedling, but unfortunately no mention was made from which kind of seed; his experiment was through interference discontinued. He made also notes on the aerophores emitted by the shallow roots as occur also in L. peruviana and other species.
DOCTERS VAN LEEUWEN () reported galled fruits caused by beetles.
Leaves are often attacked by a blue beetle: Graptodera cyanea ().


HEYNE () noted that in N. Celebes it is used for poulticing pimples. According to BURKILL () it is in Malaya generally stocked by Chinese herbalists, but its use is not clear; it was once recorded that an infusion of the root is swallowed by Malays for syphilis. In the Philippines the whole plant is used for black dye ().


The dimorphous seeds are very unusual and it would be most interesting to have information on the properties of the two seed types with respect to germination.


RAVEN 1963: p. 385. – In: Reinwardtia. map 30
VAHL 1930: Onkr. Suiker: 469. Atlas t. 444
Ridl. 1922 – In: Fl.Mal. Pen. p 827
A. & R. FERNANDES 1957 – In: Garcia de Orta. 471, 474
STEEN. 1932: Arch. Hydrobiol. p 314
BACK. & BAKH.F. 1963 – In: Fl. Java. p 260
HENTY & PRITCHARD 1973: p. 131. – In: Bot. Div. Lae, Bot. Bull. fig.
BACK. 1913: p. 20. – In: Trop. Natuur. fig.
BACK. 1914 – In: Trop. Natuur. p 61