Wayne Armstrong's On-line Description of Spirodela punctata (Lemnaceae)
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Landoltia punctata 1

(G.F.W. Meyer) Les & Crawford

Punctate Duckweed or Spotted Duckweed

Rep. Mo. Bot. Garden 9: 28; 1898.  Novon 9: 530-533; 1999.


Roots: 1-5 (rarely more than 5).

Shape of Plant Body: Flattened, oblong-obovate in outline, often asymmetrical (slightly curved laterally at basal end); dark green above with reddish-purple ventral surface; brown pigment cells (punctae) in epidermis (visible on chlorotic or dead plants).

Size: 3-5 mm long.

Veins: 3-5 (rarely 7), often obscure.

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: 2-6 (rarely more).

Habitat: Fresh water ponds, marshes and quiet streams.

Range: Generally maritime and low elevations in hot interior valleys of the western United States; eastern and southeastern U.S., forming extensive homogeneous populations in Florida and Louisiana; cosmopolitan--throughout temperate and tropical regions of both hemispheres.

Other Information:

Variable as to size of plant body and number of roots, depending on location, ecological factors and perhaps time of year; may be distinguished from Lemna spp. by its darker green plant body, conspicuous reddish ventral surface and multiple roots (sometimes only one root is present); all roots penetrating the obscure, scalelike ventral prophyllum; brown pigment cells (punctae) in epidermis, visible on dead or highly stressed plants; turions have been reported for this sp. by D.V. Richards of Humboldt State Univ.

1   D.H. Les and D.J. Crawford (1999) proposed the new genus Landoltia containing one species L. punctata, formerly Spirodela punctata (G.F.W. Meyer) C.H. Thompson. This species is morphologically intermediate between Lemna and Spirodela. According to Les & Crawford, it represents an isolated clade distinct from both Lemna and Spirodela. Les, D.H. and D.J. Crawford. 1999. "Landoltia (Lemnaceae), A New Genus of Duckweeds." Novon 9: 530-533.

Modifying The Generic Key To Fit The New Genus Landoltia

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