Southern Waternymph

By having unicellular teeth on the leaf margin, Najas guadalupensis resembles N. flexilis and N. graminea. The seeds of N. guadalupensis are pitted; those of N. flexilis are smooth. The sheaths of N. guadalupensis are rounded to slightly auriculate; those of N. graminea are deeply auriculate.

Stems often profusely branched distally, 11--90 cm ´ 0.1--2 mm; internodes 0.1--9 cm, without prickles. Leaves spreading with age, 0.3--3.3 cm, lax in age; sheath 1--3.4 mm wide, apex rounded to truncate; blade 0.2--2.1 mm wide, margins minutely serrulate, teeth 18--100 per side, apex rounded to truncateslightly auriculate, with 1--3 teeth, teeth unicellular; midvein without prickles abaxially. Flowers 1--3 per axil, staminate and pistillate on same plants. Staminate flowers in distal axils, 1.5--3 mm; involucral beaks 4-lobed, 0.2--1.3 mm; anther 1- or 4-loculed, 1--1.7 mm. Pistillate flowers in proximal axils, 1.5--4 mm; styles 0.3--1.5 mm; stigmas 4-lobed. Seeds not recurved, yellowish white with purple tinge, fusiform, 1.2--3.8 ´ 0.4--0.8 mm, apex with style situated at center; testa dull, 3 cell layers thick, pitted; aeroleareoles regularly arranged in 20--60 longitudinal rows, not ladderlike, 4--6-angled, longer than broad, end walls not raised. 2n = 12, 36, 42, 48, 54, 60.

Caulinia guadalupensis Sprengel, Syst. Veg. 1: 20. 1824