7.
Najas minor
Allioni, Flora Pedemontana. 2: 221. 1785.
Stems profusely branched near apex distally, 11--120 cm ´ 0.2--1 mm; internodes 0.5--5.8 cm, without prickles abaxially. Leaves usually recurved with age, 0.5--3.4 cm, stiff in age; sheath 1--3 mm wide, apex truncate to auriculate; blade 0.1--1.2 mm wide, margins conspicuously serrulate, teeth 7--15 per side, apex acute, with 1--2 teeth, teeth multicellular; midvein without prickles abaxially. Flowers 1--2 per axil, staminate and pistillate on same plant. Staminate flowers in distal axils, 1.9--2.2 mm; involucre 2-lobed, beaks 0.4--2.1 mm; anther 1-loculed, 0.3 mm.
Flowering summer--fall. Ponds, lakes, and slow- moving streams; 0--500 m; introduced; Ala., Del., Fla., Ga., Ill., Ind., Ky., La., Mass., Mich., Miss., Mo., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Vt., Va., W.Va.; Eurasia; Africa.
Pistillate flowers in distal to proximal axils, 2.2 mm; styles 1--1.2 mm; stigmas 2-lobed. Seeds slightly recurved, purplish, fusiform, 1.5--3 ´ 0.5--0.7 mm, apex with style situated at center; testa dull, 3 cell layers thick, pitted; aeroleareoles regularly arranged in ca. 15 longitudinal rows, ladderlike, 4-angled, broader than long, end walls not raised. 2n = 24.
Najas minor, with its mature leaves recurved and with its aeroleareoles broader than long and arranged in longitudinal rows like the rungs of a ladder, is one of the more distinctive species of Najas. Young sterile individuals resemble N. gracillima, however.
