Hygrophila corymbosa (Blume) Lindau

PHENOLOGY.— Flowering: March–May, October–December; fruiting: May.

DISTRIBUTION.— Native to southeastern Asia; naturalized in Mexico (Tamps).

HABITAT.— Riparian vegetation (irrigation canals).

ELEVATION.— 80 meters.

NOTES.— This cultivated aquatic (aquarium trade) sometimes escapes and becomes naturalized in the New World (Fig. 3A, B). The two species of Hygrophila in Tamaulipas appear in different sections of the key above; they can be readily distinguished from one another by the following couplet:

1a. Young stems and leaves of emergent shoots, calyces, corollas, and capsules pubescent with glandular trichomes; flowers in expanded dichasia or in thyrses (bearing expanded dichasia in axils of subfoliose bracts) in leaf axils; corollas purplish with white ridges, 8–16. 5 mm long; stamens 4..... H. corymbosa

1b. Young stems, leaves, calyces, corollas, and capsules glabrous or pubescent with eglandular trichomes; flowers in terminal spikes; corollas pale lavender, 4.5– 5.5 mm long; stamens 2......... H. polysperma

REPRESENTATIVE SPECIMENS.— Mpio. El Mante, irrigation water channels, 22°44ʹ54.25ʺN, 099°ʹ00ʹ26.89ʺW, A. Mora-Olivo 15620 (UAT); Mpio. El Mante, 22°43ʹ56.66ʺN, 098°58ʹ09.20ʺW, L. Alvarez 121 (UAT) .