View source for Najas

{{Treatment/ID
|accepted_name=Najas
|accepted_authority=Linnaeus
|publications={{Treatment/Publication
|title=Sp. Pl.
|place=2: 1015. 1753; Gen. Pl. ed. 5; 445, 1754
|year=1754
}}
|common_names=Bushy-pondweed;naid;water-nymph;naiade
|basionyms=
|synonyms=
|hierarchy=Najadaceae;Najas
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Najadaceae]]</div><div class="higher-taxon"><small>genus</small>[[Najas]]</div></div>
|etymology=Greek Nnaias, a water-nymph
|volume=Volume 22
|mention_page=
|treatment_page=
}}<!--

--><span class="statement" id="st-d0_s0" data-properties="whole_organism growth form or habitat;whole_organism pubescence;whole_organism location;whole_organism growth form"><b>Herbs,</b> aquatic, glabrous, submersed in fresh or brackish waters.</span> <span class="statement" id="st-d0_s1" data-properties="stem size;stem architecture;stem architecture;stem architecture"><b>Stems </b>slender, much branched, rooting at proximal nodes, sometimes armed with prickles on internodes.</span> <span class="statement" id="st-d0_s2" data-properties="sheath shape;margin shape;tooth quantity"><b>Leaves:</b> sheaths variously shaped, margins usually toothed with 1–15 teeth per side, teeth similar in size and structure to those of blades;</span> <span class="statement" id="st-d0_s3" data-properties="blade arrangement or course or shape;blade architecture;blade architecture;margin architecture or shape;margin shape or architecture;margin architecture or shape;tooth quantity;apex shape;tooth quantity;tooth architecture;cell count or size;cell size;cell architecture;tooth architecture">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.</span> <span class="statement" id="st-d0_s4" data-properties="involucre presence;involucre coloration;involucre coloration;involucre coloration or density;involucre coloration or density;involucre coloration or density;involucre coloration or density;flower architecture;flower quantity"><b>Inflorescences:</b> involucres mostly present in staminate flowers, rare in pistillate, clear, bronze, brown, light green, purple, or red-purple.</span> <span class="statement" id="st-d0_s5" data-properties="flower architecture;involucre texture;involucre presence"><b>Staminate </b>flowers subtended by membranous involucre, involucre rarely absent;</span> <span class="statement" id="st-d0_s6" data-properties="peduncle height or length or size;peduncle length">peduncle short, elongating at anthesis, pushing flower through involucre;</span> <span class="statement" id="st-d0_s7" data-properties="anther architecture;anther architecture;anther architecture">anther sessile, 1-loculed or 4-loculed.</span> <span class="statement" id="st-d0_s8" data-properties="flower architecture;flower architecture"><b>Pistillate </b>flowers sessile;</span> <span class="statement" id="st-d0_s9" data-properties="ovary architecture">ovary 1-loculed;</span> <span class="statement" id="st-d0_s10" data-properties="ovule position;ovule quantity">ovules basal, 1;</span> <span class="statement" id="st-d0_s11" data-properties="style position or structure subtype;style architecture">style terminal (arising off-center at apex of ovary and fruit in Najas gracillima), 2–4-branched.</span> <span class="statement" id="st-d0_s12" data-properties="fruit dehiscence"><b>Fruits </b>dehiscing by decay of ovary wall;</span> <span class="statement" id="st-d0_s13" data-properties="ovary wall fragility">ovary wall extremely delicate, closely enveloping seed.</span> <span class="statement" id="st-d0_s14" data-properties="seed shape;apex architecture or shape;apex orientation"><b>Seeds </b>fusiform to obovoid, apex occasionally asymmetric or recurved, aerolateareolate;</span> <span class="statement" id="st-d0_s15" data-properties="raphe position">raphe basal;</span> <span class="statement" id="st-d0_s16" data-properties="testa quantity;testa quantity">testa 3 or 10–15 cell-layers thick, hard, brittle;</span> <span class="statement" id="st-d0_s17" data-properties="cell-layer width;cell-layer texture;cell-layer fragility;cell-layer position;cell-layer quantity;cell-layer arrangement;cell-layer arrangement;row quantity;row dehiscence or orientation;end wall prominence;end wall relief">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;</span> <span class="statement" id="st-d0_s18" data-properties="">endosperm absent.</span> <span class="statement" id="st-d0_s19" data-properties="endosperm presence;x chromosome quantity">x = 6.</span><!--

-->{{Treatment/Body
|distribution=Nearly worldwide
|discussion=<p>Seeds are necessary for certain determination of species of Najas.</p><!--
--><p>Species 40 (8 in the flora).</p>
|tables=
|references={{Treatment/Reference
|id=chase1947a
|text=Chase, S. S. 1947. Preliminary Studies in the Genus Najas in the United States. Ph.D. thesis. , Cornell University.
}}{{Treatment/Reference
|id=chase1947b
|text=Chase, S. S. 1947b. Polyploidy in an immersed aquatic angiosperm. [Abstract.] Amer. J. Bot. 34: 581--582.
}}{{Treatment/Reference
|id=haynes1979a
|text=Haynes, R. R. 1979. Revision of North and Central American Najas (Najadaceae). Sida 8: 34--56.
}}{{Treatment/Reference
|id=haynes1996a
|text=Haynes, R. R. and C. B. Hellquist. 1996. New combinations in North American Alismatidae. Novon 6: 370--371.
}}{{Treatment/Reference
|id=lowden1986a
|text=Lowden, R. M. 1986. Taxonomy of the genus Najas L. (Najadaceae) in the Neotropics. Aquatic Bot. 24: 147--184.
}}{{Treatment/Reference
|id=triest1988a
|text=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.
}}{{Treatment/Reference
|id=wentz1971a
|text=Wentz, W. A. and R. L. Stuckey. 1971. The changing distribution of the genus Najas (Najadaceae) in Ohio. Ohio J. Sci. 71: 292--302.
}}
}}<!--

--><div class="treatment-key">
==Key==
<div class="treatment-key-group">
  
{| class="wikitable fna-keytable"
|-id=key-0-1
|1
|Staminate and pistillate flowers on different plants; testa pitted, 10–15 cell layers thick; midrib of leaf blade abaxially with prickles; internodes of stem usually with prickles; seeds 1.2 mm wide or wider
|[[Najas marina|Najas marina]]
|-id=key-0-1
|1
|Staminate and pistillate flowers on same plants; testa smooth or pitted, 3 cell layers thick; midrib of leaf blade abaxially without prickles; internodes of stem without prickles; seeds 1.2 mm or less wide, if 1.2 mm wide, then with smooth testa.
|[[#key-0-2| > 2]]
|-id=key-0-2
|2
|Style offset to one side of center at seed apex
|[[Najas gracillima|Najas gracillima]]
|-id=key-0-2
|2
|Style situated at center of seed apex.
|[[#key-0-3| > 3]]
|-id=key-0-3
|3
|Seeds recurved; leaves usually recurved with age.
|[[#key-0-4| > 4]]
|-id=key-0-3
|3
|Seeds not recurved; leaves spreading to ascending with age.
|[[#key-0-5| > 5]]
|-id=key-0-4
|4
|Areoles of testa broader than long, ladderlike; widespread in a variety of habitats
|[[Najas minor|Najas minor]]
|-id=key-0-4
|4
|Areoles of testa longer than broad, never ladderlike; plants of Florida and Georgia in sandy-bottomed lakes
|[[Najas filifolia|Najas filifolia]]
|-id=key-0-5
|5
|Teeth of leaf blade multicellular, 8–22 per side
|[[Najas wrightiana|Najas wrightiana]]
|-id=key-0-5
|5
|Teeth of leaf blade unicellular, 18–100 per side.
|[[#key-0-6| > 6]]
|-id=key-0-6
|6
|Testa smooth, glossy; seeds narrowly to broadly obovoid, deep brown to yellow; anthers 1-loculed
|[[Najas flexilis|Najas flexilis]]
|-id=key-0-6
|6
|Testa pitted, dull; seeds fusiform, yellowish white to greenish or reddish brown or with purple tinge; anthers 1- or 4-loculed.
|[[#key-0-7| > 7]]
|-id=key-0-7
|7
|Leaf sheath deeply auriculate at apex; restricted in North America to California
|[[Najas graminea|Najas graminea]]
|-id=key-0-7
|7
|Leaf sheath rounded to truncate slightly auriculate at apex; widespread in the flora.
|[[Najas guadalupensis|Najas guadalupensis]]
|}
</div></div><!--

-->{{#Taxon:
name=Najas
|authority=Linnaeus
|rank=genus
|parent rank=family
|synonyms=
|basionyms=
|family=Najadaceae
|distribution=Nearly worldwide
|reference=chase1947a;chase1947b;haynes1979a;haynes1996a;lowden1986a;triest1988a;wentz1971a
|publication title=Sp. Pl.
|publication year=1754
|special status=
|source xml=https://bibilujan@bitbucket.org/aafc-mbb/fna-fine-grained-xml.git/src/62857cf6bca5c4637d27b113da92d27dbf9962f4/V22/V22_555.xml
|genus=Najas
|anther architecture=4-loculed;1-loculed;sessile
|apex architecture or shape=asymmetric
|apex orientation=recurved
|apex shape=acute;acuminate
|blade architecture=armed;1-veined
|blade arrangement or course or shape=linear
|cell architecture=sharp-tipped
|cell count or size=decreasing
|cell size=large
|cell-layer arrangement=in 15-60 longitudinal rows;arranged
|cell-layer fragility=brittle
|cell-layer position=outer
|cell-layer quantity=2
|cell-layer texture=hard
|cell-layer width=thick
|end wall prominence=raised
|end wall relief=papillose
|endosperm presence=absent
|flower architecture=sessile;pistillate;staminate;staminate
|flower quantity=rare
|fruit dehiscence=dehiscing
|involucre coloration=light green;brown
|involucre coloration or density=red-purple;purple;red-purple;purple
|involucre presence=absent;absent
|involucre texture=membranous
|margin architecture or shape=serrulate;serrate
|margin shape=toothed
|margin shape or architecture=serrate to minutely
|ovary architecture=1-loculed
|ovary wall fragility=delicate
|ovule position=basal
|ovule quantity=1
|peduncle height or length or size=short
|peduncle length=elongating
|raphe position=basal
|row dehiscence or orientation=longitudinal
|row quantity=15;60
|seed shape=fusiform;obovoid
|sheath shape=variously--shaped
|stem architecture=armed;rooting;branched
|stem size=slender
|style architecture=2-4-branched
|style position or structure subtype=terminal
|testa quantity=10;15
|tooth architecture=unicellular;multicellular
|tooth quantity=1;3
|whole_organism growth form=herb
|whole_organism growth form or habitat=aquatic
|whole_organism location=submersed
|whole_organism pubescence=glabrous
|x chromosome quantity=6
}}<!--

-->[[Category:Treatment]][[Category:Najadaceae]]