''Helanthium tenellum'', the pygmy chain sword, is a species of plants in the
Alismataceae. It is native to the eastern United States (from
Texas to
Florida, north to
Michigan and
Massachusetts), southern Mexico (
Chiapas
Chiapas (; Tzotzil language, Tzotzil and Tzeltal language, Tzeltal: ''Chyapas'' ), officially the Free and Sovereign State of Chiapas ( es, Estado Libre y Soberano de Chiapas), is one of the states that make up the Political divisions of Mexico, ...
,
Veracruz), West Indies (Cuba, Jamaica,
Hispaniola
Hispaniola (, also ; es, La Española; Latin and french: Hispaniola; ht, Ispayola; tnq, Ayiti or Quisqueya) is an island in the Caribbean that is part of the Greater Antilles. Hispaniola is the most populous island in the West Indies, and th ...
), Central America, South America (from Guyana to Argentina)
Description
The
leaves
A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
of ''H. tenellum'' are narrowly elliptical or
lanceolate. At different times during the plant's
life cycle, the blade of the leaf is scarcely distinguishable from the
petiole, while at other times the petiole is 10 to 15 times as long as the blade, which may be 1–4 cm long and 0.2–1 cm wide, with a pointed tip. The base is decurrent to the petiole and has between one and three veins.
The stem is thin, erect, often curved, and may be 3–20 cm long. In small plants, the stem ends in a single
inflorescence (umbel or coil); in larger plants the inflorescence is
racemose, composed of two
whorls
A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs).
Whorls in nature
File:Photograph and axial plane floral d ...
placed one above the other.
Bracts are free and 2–6 mm long in the first whorl. Pedicels are 1–3.5 cm long.
Sepals
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...
are 3 mm long, membraneous, and usually have five fine ribs. During ripening, the
sepals
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...
enlarge and reach a length of up to 6 mm and fully cover the aggregate
fruit. A specimen may have six to nine
stamens, each about 1 mm long.
Anthers
The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10
Morphology and terminology
A stamen typically consists of a stalk called the filam ...
are 0.25 mm wide by 2.25 mm long, which is three times shorter than the filaments. It may have sixteen to eighteen
pistils. The
achenes are compressed, and arched in the apical part; they are (0.9) – 1.1 – (1.3) mm long, and black, with three lateral ribs. The basis of the
stylar beak is under the level of the tip of the
nutlet
A nut is a fruit consisting of a hard or tough nutshell protecting a kernel which is usually edible. In general usage and in a culinary sense, a wide variety of dry seeds are called nuts, but in a botanical context "nut" implies that the shell ...
and may be 0.1–0.3 mm long.
It propagates by sending out
runners
Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot. Running is a type of gait characterized by an aerial phase in which all feet are above the ground (though there are exceptions). This is ...
and will also flower when grown emersed.
Conservation status in the United States
It is endangered in
Connecticut,
Illinois,
Indiana,
Kentucky, and
Michigan.
In the aquarium
''Helanthium tenellum'' is a common
aquarium plant
Aquascaping is the craft of arranging aquatic plants, as well as rocks, stones, cavework, or driftwood, in an aesthetically pleasing manner within an aquarium—in effect, gardening under water. Aquascape designs include a number of distinct styl ...
with a large variation in shapes and sizes kept by people for their aesthetic appeal. Its care is undemanding and it can adapt to a large range of conditions.
References
External links
Photo of herbarium specimen collected in Missouri in 1845, ''Helanthium tenellum''Flora of North America, ''Echinodorus tenellus''US Department of Agriculture plant profile, ''Echinodorus tenellus''*
ttp://www.efloras.org/florataxon.aspx?flora_id=11&taxon_id=222000054 Flora of Missouri, ''Echinodorus tenellus''AquaHobby, The Age of Aquariums, ''Echinodorus tenellus''
{{Taxonbar, from=Q15583933
Alismataceae
Flora of Northern America
Flora of Southern America
Aquatic plants
Plants described in 1830