Holly Leaved Naiad

With its prickly internodes and prickles along the abaxial surface of the leaves, Najas marina is the easiest of our Najas to recognize. Over its entire range, the species displays considerable morphologic variability (L. Triest et al. 1986), giving cause for ten subspecies to be recognized (L. Triest 1988). In North America, however, variability is relatively minor, so I am recognizing the taxon at the specific level only (R. R. Haynes 1979). The species should be studied over its entire range, utilizing a variety of approaches, to determine adequately what, if any, infraspecific taxa should be recognized.

Stem up to 50-55 cm long, more than 1 mm broad, rather coarse; spiny, the lower internodes up to 10 cm long. Leaves oblong-linear, 1-3.5 x 2-6 mm, prominently spinose-dentate on the margins and the midrib on dorsal side. Sheath short, rounded, entire or with 1-3 inconspicuous spines. Flowers solitary. Male flowers enclosed in spathe, neck cylindrical, edge somewhat lobed; anther 4-thecous. Female flowers without spathe, style with 2-3 stigmas. Fruits ellipsoid, 23-5 x 1-4 mm. Seeds pale yellow-brownish. Areoles irregular in shape and size.

Stems branched distally, 6--45 cm ´ 0.5--4 mm; internodes 0.3--11 cm, usually with prickles. Leaves spreading to ascending with age, 0.5--3.9 cm, stiff in age; sheaths 2--4.4 mm wide, apex acute; blade 0.4--4.5 mm wide, margins coarsely serrate, teeth 8--13 per side, apex acute, with 1 tooth, teeth multicellular; midvein with prickles abaxially. Flowers 1 per axil, staminate and pistillate on different plants. Staminate flowers in distal to proximal axils, 1.7--3 mm; involucral beaks 2-lobed, 0.3--0.7 mm; anthers 4-loculed, 1.7--3 mm. Pistillate flowers in distal to proximal axils, 2.5--5.7 mm; styles 1.2--1.7 mm; stigmas 3-lobed. Seeds not recurved, reddish brown, ovoid, 2.2--4.5 ´ 1.2--2.2 mm, apex with style situated at center; testa dull, 10--15 cell layers thick, pitted; areoles irregularly arranged, not in distinctive rows, not ladderlike, 3--4-angled, longer than broad, end walls slightly raised. 2n = 12 (Europe).

Distribution: Most of Europe, Asia, N. Africa, Australia, N. and S. America.

Ariz., Calif., Fla., Ind., Mich., Minn., Nev., N.Y., N.Dak., Ohio, Pa., S.Dak., Tex., Utah, Wis.; Mexico; West Indies; Central America (El Salvador, Panama); South America; Eurasia.

Fl. Per.: March-December.

Flowering summer--fall.

Brackish or highly alkaline waters of ponds and lakes; 0--1000m.

Najas gracilis (Morong) Small