Najas arguta

• Description
• Taxonomy
• Similar Species
• More Info
• Further Reading
• Notes

Description

Family Hydrocharitaceae

Herbs, annual or perennial , caulescent or without evident stem, glabrous or pubescent , entirely submersed , with both submersed and floating leaves, or with submersed stolons and emergent leaves, in fresh, brackish , or marine waters; turions rarely present. Stems rhizomatous , creeping , with abbreviated erect axis at nodes, or erect, leafy, elongate . Leaves basal, alternate, opposite, or whorled , sessile or petiolate ; stipules sometimes present, forming tubular sheath around stem; blade margins entire or serrate; veins 1--many. Inflorescences axillary , terminal , or scapose , 1-flowered or cymose , subtended by spathe ; spathe a 2-fid bract or pair of opposite bracts. Flowers unisexual , staminate and pistillate on same plants or on different plants, often with rudiments of opposite type, or bisexual , actinomorphic , rarely slightly zygomorphic; perianth epigynous , free , mostly 6-parted, then differentiated into sepals and petals, rarely 3-parted, then petals absent in Thalassia and Halophila; stamens (0--) 2--many in 1 or more whorls (inner often staminodial), epigynous, distinct or ± connate ; pollen spheric, in monads or tetrads or in slender chains; ovary 0--1, if present, inferior, 2--6[--16]-carpellate, 1-locular or falsely 6--9-locular; placentation parietal . Fruits berrylike. Seeds many, fusiform , ellipsoid , ovoid , or spheric; seed coat glabrous, papillose , or echinate .

Genera 17, species ca. 76 (10 genera, 14 species in the flora ) : nearly worldwide.

Hydrocharitaceae, like other members of the Alismatidae, have one or more (fewer than 20) scales (intravaginal squamules ) in the axils of their leaves. These scales (or hairs in some taxa) secrete mucilage and are without any venation . The structures are often referred to as "squamulae intravaginales" or "intravaginal scales" in the literature.[1]

Genus Najas

Herbs, aquatic , glabrous , submersed in fresh or brackish waters. Stems slender, much branched, rooting at proximal nodes, sometimes armed with prickles on internodes. Leaves: sheaths variously shaped, margins usually toothed with 1--15 teeth per side, teeth similar in size and structure to those of blades ; blade linear, 1-veined, sometimes armed with prickles on midvein abaxially, margins usually serrate to minutely serrulate with 5--100 teeth per side, apex acute to acuminate, with 1--3 teeth, teeth multicellular, formed by layers of cells decreasing in cell number distally, terminated by large, sharp-tipped cell, or teeth unicellular. Inflorescences: involucres mostly present in staminate flowers , rare in pistillate , clear, bronze, brown, light green, purple, or red-purple. Staminate flowers subtended by membranous involucre, involucre rarely absent; peduncle short, elongating at anthesis , pushing flower through involucre; anther sessile, 1- or 4-loculed. Pistillate flowers sessile; ovary 1-loculed; ovules basal, 1; style terminal (arising off-center at apex of ovary and fruit in Najas gracillima), 2--4-branched. Fruits dehiscing by decay of ovary wall; ovary wall extremely delicate, closely enveloping seed. Seeds fusiform to obovoid , apex occasionally asymmetric or recurved, aerolateareolate; raphe basal; testa 3 or 10--15 cell layers thick, hard, brittle; aeroleareoles formed by outer two cell layers of testa, irregularly arranged or in 15--60 longitudinal rows , end walls often raised, giving testa papillose appearance ; endosperm absent. x = 6.

Species 40: nearly worldwide.

Seeds are necessary for certain determination of species of Najas.[2]

Taxonomy

Notes

Name Status: Accepted Name . Latest taxonomic scrutiny: Govaerts R., 06-Jan-2005.

Similar Species

Members of the genus Najas

ZipcodeZoo has pages for 165 species, subspecies, varieties, forms, and cultivars in this genus. Here are just 100 of them:

N. affinis · N. alagnensis · N. ancistrocarpa · N. arcana · N. arguta · N. arguta var. podostemon · N. arguta var. tenera · N. armata · N. arsenariensis · N. australis · N. baldwinii · N. bengalensis · N. brevistyla · N. browniana · N. caespitosa · N. caespitosus · N. canadensis · N. celebica · N. chinensis · N. conferta · N. delilei · N. dichotoma · N. falciculata · N. filifolia (Needleleaf Waternymph) · N. flexilis (Northern Water-Nymph) · N. flexilis caespitosus · N. flexilis robusta · N. flexilis var. congesta · N. flexilis var. curassavica · N. flexilis var. fusiformis (Slender Naiad) · N. flexilis var. gollmeriana · N. flexilis var. guadalupensis · N. flexilis var. guadelupensis · N. flexilis var. punctata · N. flexilis var. tenera · N. fluviatilis · N. foveolata · N. fragilis · N. fucoides · N. gracilis · N. gracillima (Slender Waternymph) · N. graminea (Ricefield Waternymph) · N. gramineae · N. graminea var. longidentata · N. graminea var. recurvata · N. grossareolata · N. guadalupensis (Guadalupe Waternymph) · N. guadalupensis f. florida · N. guadalupensis f. floridana · N. guadalupensis floridana (Florida Waternymph) · N. guadalupensis guadalupensis (Guadalupe Waternymph) · N. guadalupensis muenscheri (Muenscher's Waternymph) · N. guadalupensis olivacea (Guadalupe Waternymph) · N. guadalupensis subsp. floridana (Florida Waternymph) · N. guadalupensis subsp. muenscheri (Muenscher's Waternymph) · N. guadalupensis subsp. olivacea (Guadalupe Waternymph) · N. guadalupensis var. florida · N. guadalupensis var. guadalupensis (Southern Naiad) · N. guadelupensis · N. guadelupensis var. curassavica · N. guadelupensis var. floridana · N. guadelupensis var. muenscheri · N. guadelupensis var. olivacea · N. hagerupi · N. hagerupii · N. halophila · N. heteromorpha · N. hoehnei · N. horrida · N. indica · N. intermedia · N. interrupta · N. intramongolica · N. japonica · N. kingii · N. kurziana · N. lacerata · N. laevis · N. latifolia · N. leichhardtii · N. liberiensis · N. lobata · N. madagacariensis · N. madagascariensis · N. major · N. major var. gracilis · N. major var. microcarpa · N. major var. polonica · N. malesiana · N. marina (Holly-Leaved Waternymph) · N. marina aculeolata · N. marina armata · N. marina arsenariensis · N. marina brachycarpa · N. marina commersonii · N. marina ehrenbergii · N. marina intermedia · N. marina latior · N. marina microcarpa · N. marina subsp. armata

More Info

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Further Reading

• Ancibor, E. 1979. Systematic anatomy of vegetative organs of the Hydrocharitaceae. Bot. J. Linn. Soc. 78: 237--266.
• Catling, P. M. and W. G. Dore. 1982. Status and identification of Hydrocharis morsus-ranae and Limnobium spongia (Hydrocharitaceae) in northeastern North America. Rhodora 84: 523--545.
• Cook, C. D. K. 1982. Pollinating mechanisms in the Hydrocharitaceae. In: J.-J. Symoens et al., eds. 1982. Studies on Aquatic Vascular Plants. Brussels. Pp. 1--15.
• Godfrey, R. K. and J. W. Wooten. 1979. Aquatic and Wetland Plants of Southeastern United States:. Monocotyledons. Athens, Ga.
• Hartog, C. den. 1970. The Sea-grasses of the World. Amsterdam.
• Chase, S. S. 1947b. Polyploidy in an immersed aquatic angiosperm. [Abstract.] Amer. J. Bot. 34: 581--582.
• Chase, S. S. 1947. Preliminary Studies in the Genus Najas in the United States. Ph.D. thesis. , Cornell University.
• Haynes, R. R. and C. B. Hellquist. 1996. New combinations in North American Alismatidae. Novon 6: 370--371.
• Haynes, R. R. 1979. Revision of North and Central American Najas (Najadaceae). Sida 8: 34--56.
• Lowden, R. M. 1986. Taxonomy of the genus Najas L. (Najadaceae) in the Neotropics. Aquatic Bot. 24: 147--184.
• Triest, L. 1988. A revision of the genus Najas L. (Najadaceae) in the Old World. Mém. Acad. Roy. Sci. Belgique, Cl. Sci. (8° ), n. s. 22: 1--172, 29 plates.
• Wentz, W. A. and R. L. Stuckey. 1971. The changing distribution of the genus Najas (Najadaceae) in Ohio. Ohio J. Sci. 71: 292--302.

Notes

Contributors

• Bisby, F.A., Y.R. Roskov, M.A. Ruggiero, T.M. Orrell, L.E. Paglinawan, P.W. Brewer, N. Bailly, J. van Hertum, eds (2007). Species 2000 & ITIS Catalogue of Life: 2007 Annual Checklist. Species 2000: Reading, U.K.
• World Checklist of Selected Plant FamiliesOct , 2007.

Identifiers

• Biodiversity Heritage Library NamebankID: 8645688
• Catalogue of Life Accepted Name Code: Kew-308223
• International Plant Names Index (IPNI) ID: 602989-1
• Zipcode Zoo Species Identifier: 3879887

Footnotes

1. Robert R. Haynes "Hydrocharitaceae". in Flora of North America Vol. 22. Oxford University Press. Online at EFloras.org. [back]
2. Mark A. Hershkovitz & Sean B. Hogan "Najas". in Flora of North America Vol. 22. Oxford University Press. Online at EFloras.org. [back]

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