Lemnaceae - Images of Lemna aequinoctialis
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Lemna aequinoctialis

Dorsal view of several budding plants showing prominent apical papules.

Seeds of Lemna aequinoctialis collected by Mr. Wolffia on the Island of St. John (U.S. Virgin Islands). They are small enough to easily pass through the "eye" of an ordinary sewing needle. Note the longitudinal ribs on the seeds. In the closely related Lemna perpusilla, the seeds have up to twice as many faint longitudinal ribs. Since seeds are rarely collected, they are not very useful in identifying species of duckweeds.

Seeds of an unidentified Lemna, probably L. aequinoctialis. Seven
longitudinal ribs (marked by red dots) can be seen in the right seed.

Seeds of Lemna perpusilla collected on Staten Island by Steve Young, Botanist at the New York Natural Heritage Program. The seeds are similar to the tropical L. aequinoctialis in the previous photo, except they have twice as many faint, longitudinal ribs. Both L. perpusilla and L. aequinoctialis readily produce seeds, compared with most other duckweed species. Seeds of L. perpusilla can overwinter in cold climates, while those of L. aequinoctialis generally germinate quickly in warmer waters. In addition, L. aequinoctialis does not produce flowers and fruit in cooler climates. The seeds of both species are less than one mm in length. To appreciate their minute size, compare one mm with three grains of table salt in the following image.

Microscopic view of three cuboidal grains of ordinary table salt (sodium chloride or NaCl). All three grains are just over one millimeter in length (red bar). Grains of table salt vary slightly in size, but three average grains stacked together adds up to approximately one mm. If three grains equal one millimeter in length, then a single grain is approximately 0.3 mm or 0.03 cm on a side.

Lemna aequinoctialis from the Sierra San Francisco of Baja California. This view shows the basal root sheath with two lateral wings and a one-seeded fruit (utricle) protruding from a lateral budding pouch. The number of longitudinal ribs on the seed (faintly visible through the transparent pericarp) indicates that this species is L. aequinoctialis and not L. perpusilla. The head of an ordinary straight pin is used for a size relationship. It is 1.5 mm in diameter.

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