''Micranthemum micranthemoides'' (syn. ''Hemianthus micranthemoides''), commonly known as Nuttall's mudflower or pearlweed in aquascaping, is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

species of subaquatic

Micranthemum ''Micranthemum'' is a genus of flowering plants belonging to the family Linderniaceae. Its native range is Eastern USA to Tropical and Subtropical America. Species Species: *''Micranthemum arenarioides'' *''Micranthemum bryoides'' *''Micrant ...

that previously inhabited wet areas from

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

. It is commonly misidentified as a similar species, '' Micranthemum glomeratum'', in aquascaping.

Description

''Micranthemum micranthemoides'' was a small subaquatic glabrous

annual Annual may refer to: *Annual publication, periodical publications appearing regularly once per year **Yearbook **Literary annual *Annual plant *Annual report *Annual giving *Annual, Morocco, a settlement in northeastern Morocco *Annuals (band), a ...

that exhibited creeping stems and ascending branches. ''Micranthemum micranthemoides'' grew 5-20 cm in height. ''Micranthemum micranthemoides'' had opposite, elliptic leaves measuring 2–5 mm. Leaves were entire. Flowers were both solitary and axillary. Each flower's corolla was white and measured 2 mm. Flowers contained two stamens, which were inserted around the corolla's throat. ''Micranthemum micranthemoides'' flowered from September to October. Its seeds were oblong to narrowly obconic.

Distribution and habitat

''Micranthemum micranthemoides'' previously occurred in the

mid-atlantic region The Mid-Atlantic is a region of the United States located in the overlap between the nation's Northeastern and Southeastern states. Traditional definitions include seven U.S. states: New York, New Jersey, Pennsylvania, Delaware, Maryland, Virgi ...

of the United States. It grew in wet areas from Virginia to New York. Before its extinction, it was a rare occurrence in tidal

mudflats Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal ...

and in the intertidal zone of river estuaries. It is said to have been highly specialized to these habitats. ''Micranthemum micranthemoides'' grew in sandy and gravelly substrates. It was last seen on 13 September 1941 by Fernald & Long.

Misidentification

Plants labeled ''Micranthemum micranthemoides'' or ''Hemianthus micranthemoides'' are commonly sold in aquascaping as "pearlweed", but are not truly of this species. When examined, these plants sold as pearlweed were actually of a similar species, ''Micranthemum glomeratum'', which is native to

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

. This misidentification was confirmed by Academy of Natural Sciences Botany Curator Emeritus Ernie Schuyler when the aquascaping plants were compared to herbarium specimens and descriptions of ''Micranthemum micranthemoides''. ''Micranthemum micranthemoides'' probably has never been cultivated as an aquarium plant.

References

Scrophulariaceae Aquatic plants Plants described in 1891 {{Scrophulariaceae-stub