Limnophila
Prodr., 442. 1810.
Herbs, perennial [annual], paludal or aquatic, emergent. Stems erect [prostrate, creeping], hairy or glabrous. Leaves cauline, opposite or whorled, dimorphic; petiole present or absent; blade not fleshy, not leathery, margins of submerged leaves pinnatifid, of aerial leaves entire, serrate, or pinnatifid. Inflorescences terminal or axillary, racemes or flowers solitary, rarely paired [or spikes]; bracts present or absent. Pedicels present or absent; bracteoles present or absent. Flowers bisexual, chasmogamous or cleistogamous; sepals 5, basally connate, calyx bilaterally symmetric, tubular, lobes triangular or lanceolate [ovate]; corolla blue, blue-purple, or white, bilaterally symmetric, bilabiate, tubular or funnelform, tube base not gibbous or spurred, lobes 4 or 5, abaxial 3, adaxial 1 or 2; stamens 4, basally adnate to corolla, didynamous, filaments glabrous or hairy; staminode 0; ovary 2-locular, placentation axile; stigma capitate, 2-lobed. Fruits capsules, dehiscence septicidal. Seeds 20–200, brown to dark brown, conic to cylindric, wings absent. × = 17.
Distribution
Asia, Africa, Pacific Islands, Australia, introduced also in South America.
Discussion
Species 40 (2 in the flora).
The two species recognized here could be difficult to distinguish throughout their ranges; intermediate plants, which are believed to be hybrids, have been found.
Limnophila is closely related to Hydrotriche Zuccarini, a small genus of aquatic plants native to Madagascar. Together they form a group sister to Gratiola in Gratioleae (D. Estes and R. L. Small 2008).
Selected References
Lower Taxa
Key
| 1 | Pedicels 3–8 mm in flower, 5–12 mm in fruit; bracteoles 1–3.5 mm; corolla tubes 4–5(–8) mm; cleistogamous flowers absent. | Limnophila indica |
| 1 | Pedicels 0–2 mm in flower, 0–4 mm in fruit; bracteoles 0–1.5 mm; corolla tubes 8–10 mm; cleistogamous flowers present, submerged. | Limnophila sessiliflora |