Micranthemum micranthemoides
Extinct subaquatic plant from Mid-Atlantic US tidal mudflats.
Here is the rewritten encyclopedia entry:
**Micranthemum micranthemoides**, also called Nuttall's mudflower and once known as *Hemianthus micranthemoides*, is an extinct aquatic plant. It was a small, smooth annual that grew along wet areas between Virginia and New York. The plant had creeping stems with upright branches, reaching 5 to 20 cm tall. Its leaves were opposite, elliptical, and entire, measuring 2 to 5 mm. White flowers, each 2 mm across, grew singly in the leaf axils and had two stamens set near the throat of the corolla. Flowering occurred from September to October, and the seeds were oblong to narrowly obconic.
This species was found only in the Mid-Atlantic United States, in tidal mudflats and the intertidal zones of river estuaries. It was highly specialized to these freshwater habitats and could not tolerate salt. It grew on sandy or gravelly substrates. The last confirmed sighting was on September 13, 1941, by Fernald and Long, along the intertidal portions of the Delaware, Pocomoke, Wicomico, Potomac, Anacostia, Chickahominy, and Hudson rivers. The name *Micranthemum micranthemoides* was once applied to a broader group of plants from the Northeast, Southeast, and West Indies, but that group has since been divided into separate species.
In the aquarium trade, plants sold as "pearlweed" under the names *Micranthemum micranthemoides* or *Hemianthus micranthemoides* are actually a different species, *Micranthemum glomeratum*, which is native to Florida. This mistake was confirmed by Ernie Schuyler, Botany Curator Emeritus at the Academy of Natural Sciences, after comparing the aquarium plants to herbarium specimens and original descriptions. It is likely that the true *Micranthemum micranthemoides* was never grown in cultivation.
Quick Facts
- Genus
- Micranthemum
- Species
- micranthemoides
Facts from the source article.
Lore & Background
Micranthemum micranthemoides was a small subaquatic glabrous annual with creeping stems and ascending branches, growing 5–20 cm in height. It had opposite, elliptic leaves measuring 2–5 mm, entire margins, and solitary or axillary flowers. Each flower had a white corolla 2 mm in diameter, containing two stamens inserted around the corolla's throat. It flowered from September to October, and its seeds were oblong to narrowly obconic.
This species previously occurred in the Mid-Atlantic region of the United States, growing in wet areas from Virginia to New York. Before its extinction, it was a rare inhabitant of tidal mudflats and the intertidal zone of river estuaries, highly specialized to these habitats. It grew in sandy and gravelly substrates. It was last seen on 13 September 1941 by Fernald & Long, found in the intertidal portions of the Delaware, Pocomoke, Wicomico, Potomac, Anacostia, Chickahominy, and Hudson rivers. It was restricted to freshwater estuarine shores, indicating an intolerance to salinity.
The name Micranthemum micranthemoides was previously attributed to a larger species concept including plants from the Northeast, Southeast, and West Indies, but has since been split into distinct entities.
Reader's Guide
Micranthemum micranthemoides holds significance primarily as an extinct species that was highly specialized to tidal mudflats and intertidal zones of river estuaries in the Mid-Atlantic United States. Its last confirmed sighting was on 13 September 1941 by botanists Fernald & Long, after which it was never recorded again. The species is also notable for a persistent misidentification in the aquascaping trade: plants sold as 'pearlweed' under the names Micranthemum micranthemoides or Hemianthus micranthemoides are actually Micranthemum glomeratum, a similar species native to Florida. This misidentification was confirmed by Academy of Natural Sciences Botany Curator Emeritus Ernie Schuyler when aquarium plants were compared to herbarium specimens and descriptions of the true Micranthemum micranthemoides. According to the article, Micranthemum micranthemoides probably has never been cultivated as an aquarium plant. Its legacy thus lies in its extinction and the ongoing confusion in the aquarium hobby, where a living species is traded under the name of a lost one.
Did You Know?
- It grew only in freshwater estuarine shores, indicating an intolerance to salinity.
- Plants sold as 'pearlweed' in aquascaping are actually Micranthemum glomeratum, not this extinct species.
- The species was restricted to the intertidal zones of rivers including the Delaware, Potomac, and Hudson.
More in Aquarium and Aquatic Plants, Part 2 1-24
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