Flora of Usina São José, Igarassu, Pernambuco (Brazil): Lythraceae J. St.-Hil. and Onagraceae Juss

Lythraceae comprises about 30 genera and 600 species widely distributed in tropical and subtropical regions, while Onagraceae comprises 22 genera and about 660 species distributed in temperate and subtropical areas, predominantly in Americas. The aim of this work was to realize the taxonomic study of Lythraceae and Onagraceae species from Usina São José, Igarassu, Pernambuco (Brazil), an Atlantic forest remnant. Fieldworks and visits to herbaria HST, HUEFS, IPA, JPB, PEUFR and UFP were conducted between 2018 and 2019. Three Lythraceae species were recognized: Cuphea carthagenensis (Jacq.) J.F. Macbr., C. flava Spreg. and Rotala ramosior (L.) Koehne, and three Onagraceae species: Ludwigia erecta (L.) H. Hara, L. hyssopifolia (G. Don) Exell and L. octovalvis (Jacq.) P.H. Raven. Rotala ramosior is a new record for Brazil. Morphological descriptions, an identification key, phenological period, geographic distribution, taxonomic notes, photographs and illustrations of diagnostic characters are presented herein. The relevant morphological characters for species identification are phyllotaxy, indumentum of stems, shape and indumentum of leaves, petals color and apex, capsule shape, seeds arrangement and raphe size.