Ludwigia

Rocha, Amanda Macêdo & Melo, José Iranildo Miranda de, 2020, Diversity and distribution of Ludwigia (Onagraceae) in Paraíba State, Northeastern Brazil, European Journal of Taxonomy 639, pp. 1-24 : 6

Key to Ludwigia species recorded in the Paraíba State, Brazil

1. Leaves petiolate, leaf blade orbicular; petals white with yellow spot at the base .............................. ..................................................................................................... L. helminthorrhiza (Mart.) H.Hara

– Leaves subsessile to sessile, leaf blade elliptical to lanceolate or oblong-lanceolate to lanceolatelinear; petals entirely yellow (golden yellow or pale) ...................................................................... 2

2. Flowers pentamerous sometimes hexamerous; endocarp horseshoe-shaped ..................................... ............................................................................................................... L. leptocarpa (Nutt.) H.Hara

– Flowers tetramerous; when present, endocarp is never horseshoe-shaped ....................................... 3

3. Petals with emarginate apex; raphe inflated, with diameter equal in size to the body of the seed ................................................................................................... L. octovalvis (Jacq.) P.H.Raven

– Petals with acute or attenuate apex; raphe non-inflated, with diameter narrower than the body of the seed ................................................................................................................................................... 4

4. Fruits cylindrical; seeds usually pluriseriate and not embedded in the upper part of capsule, and uniseriate and embedded in endocarp in the lower part of capsule .................................................... ............................................................................................................. L. hyssopifolia (G.Don) Exell

– Fruits tetrangular; seeds all pluriseriate and not embedded in endocarp .......................................... 5

5. Leaf blade chartaceous; high nectariferous disk; capsule obconic ............ L. nervosa (Poir.) H.Hara – Leaf blade membranaceous; plain nectariferous disk; capsule oblongoid ...... L. erecta (L.) H.Hara.