Pontederia subg. Eichhornia (Kunth) M.Pell. & C.N.Horn, 2018

Pellegrini, Marco O. O., Horn, Charles N. & Almeida, Rafael F., 2018, Total evidence phylogeny of Pontederiaceae (Commelinales) sheds light on the necessity of its recircumscription and synopsis of Pontederia L., PhytoKeys 108, pp. 25-83 : 25

4. Pontederia subg. Eichhornia (Kunth) M.Pell. & C.N.Horn comb. et stat. nov. Fig. 8

Eichhornia Kunth, Enum. Pl. 4: 129. 1843. Type species. Eichhornia azurea (Sw.) Kunth. (≡ P. azurea Sw.).

Leptosomus Schltdl., Abh. Naturf. Ges. Halle 6: 174. 1862. Type species. Leptosomus natans (P.Beauv.) Schltdl. (≡ P. natans P.Beauv.).

Description.

Herbs perennial, aquatic, procumbent-emergent. Rhizome short and generally inconspicuous. Stems trailing, spongy, branched to unbranched. Sessile leaves late deciduous, sometimes persistent in mature plants. Petiolate leaves distichously-alternate, evenly distributed along stem, emergent, ligule truncate, petioles not-inflated, blades cordate to ovate or obovate to broadly obovate to rounded. Main florescences (inflorescences) axillary or terminal, pedunculate; inflorescence leaf without an inflated leaf-sheath; basal bract tubular; cincinni alternate, 1-3-flowered, sessile to subsessile, internodes contracted. Flowers sessile, chasmogamous, tristylous or pseudo-homostylous, zygomorphic, non-enantiostylous, perianth connate forming a tube, infundibuliform, revolute at post-anthesis, deliquescent and loosely enclosing the developing fruit, lobes 3 superior and 3 inferior, rarely 5 superior and 1 inferior, the central superior lobe with a nectar guide, consisting of 2 yellowish-green to green spots, generally surrounded by a dark purple to bluish-purple, rarely white blur, coiling or post-anthesis; stamens dimorphic, filaments free from each other, J-shaped, glandular-pubescent, anthers dorsifixed, rimose; ovary with 3 fertile locules, multi-ovulate, septal nectaries present, style glabrous, stigma capitate to trilobate. Capsules loculicidal or with irregular dehiscence, ellipsoid to oblongoid; anthocarp thin, smooth. Seeds subglobose to broadly oblongoid, testa longitudinally winged.

Circumscription.

Pontederia subg. Eichhornia is composed of four species. All species occur in permanently or seasonal water bodies, growing as procumbent-emergent and resembling in habit some members of P. subg. Monochoria and P. subg. Pontederia . The members of this subgenus are peculiar within Pontederia s.l. due to their late deciduous sessile leaves (sometimes persistent throughout the plant’s entire lifespan), perianth infundibuliform, revolute at post-anthesis, deliquescent and loosely enclosing the developing fruit, glandular-pubescent filaments, glabrous styles and anthocarp thin and smooth.

Distribution.

Mainly Neotropical, except for P. natans , which is restricted to continental Africa and Madagascar.

Figures

Figure 8. Pontederia subg. Eichhornia (Kunth) M. Pell. & C. N. Horn. A-B habit: A habit of P. heterosperma (Alexander) M. Pell. & C. N. Horn, showing the emerged petiolate leaves B habit of P. diversifolia (Vahl) M. Pell. & C. N. Horn, showing the floating petiolate leaves C-F inflorescence: C 2 - 3 - flowered inflorescences of P. diversifolia, showing the flowers with a yellow nectar guide in the posterior perianth lobes D 1 - flowered inflorescence of P. natans P. Beauv., showing the lack of a nectar guide E inflorescence of P. heterosperma, showing the lack of nectar guides in the posterior perianth lobes F morphological variation of inflorescences and perianth colour of P. azurea Sw G front view of a flower of P. azurea H front view of a flower of P. natans. A, B by O. Gaubert C by A. S. Castro D by P. Birnbaum E by H. Medeiros F by L. O. A. Teixeira G by M. O. O. Pellegrini and I by T. C. Buruwate.