Wayne Armstrong's On-line Description of Lemna aequinoctialis (Lemnaceae)
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Lemna aequinoctialis

Welwitsch

Tropical Duckweed

Ann. Conselho Ultram. 55: 578; 1859.

Description:

Roots: One root, base of root sheath with 2 lateral winglike appendages.

Shape of Plant Body: Flattened, obovate-elliptical in outline, asymmetrical (oblique or laterally curved) at basal end; dorsal surface with prominent apical papule and nodal papule (above root).

Size: 2-3.5 mm long.

Veins: Obscurely 3-veined.

Budding Pouch Position: 2 lateral pouches on either side of basal end.

Flower (Fruit) Position: Within membranous, cuplike spathe (open on one side) inside budding pouches.

Arrangement of Clonal Clusters: Solitary or 2-several connected.

Habitat: Fresh water ponds, marshes and quiet streams.

Range: Rare in the Pacific Northwest; generally warm climates at low elevations in desert areas and hot interior valleys of California, Baja California and Arizona; throughout temperate and tropical regions of both hemispheres.

Other Information:

The winged appendages on the root sheath separate this sp. from other Lemna spp. in North America; in addition the roots are typically 3 cm or less in length, shorter that other Pacific Coast spp. The closely related L. perpusilla Torrey of the eastern United States has seeds with 35-60 obscure ribs and 2-3 papules above the node; although seeds are rarely collected, those of L. aequinoctialis have 8-22 longitudinal ribs. In addition, the seeds of L. aequinoctialis typically fall out of the fruit wall after ripening, while those of L. perpusilla tend to remain within the fruit wall at maturity.

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