Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.
1 Leaves < 5× as long as wide; lower side of the midvein with 0-6 prickles. | |
1 Leaves > 5× as long as wide; lower side of the midvein with 0 prickles |
2 Leaves at only 2-3 closely spaced nodes at the summit of the stem, appearing verticillate or whorled; leaves to 10 cm long; [saltwater]; [subfamily Hydrilloideae] | |
5 Leaves mostly 1-2 cm long, toothed with stout, sharp teeth on the margins and also on conical bases along the midrib beneath; fresh leaves noticeably rough to the touch; leaf whorls crowded on terminal portions of stems, remote on older stems; petals translucent, 2-5 mm long; [subfamily Hydrilloideae] | |
6 Leaves < 5× as long as wide; lower side of the midvein with 0-6 prickles. | |
6 Leaves > 5× as long as wide; lower side of the midvein with 0 prickles | |
8 Plant emergent or floating; [subfamily Hydrocharitoideae] | |
9 Petals broadly ovate, > 1.5× as long as the sepals; filaments fused for < 1/2 their length; larger aerenchyma (as measured at 1 mm from the midvein on the underside of the leaf) 0.1-0.5 mm across; stranded plants with deeply cordate leaves similar in shape to the floating leaves, with strongly arcing primary veins | |
9 Petals linear, < 1.5× as long as the sepals; filaments fused for > 1/2 their length; larger aerenchyma (as measured at 1 mm from the midvein on the underside of the leaf) 0.4-1.6 mm across; stranded plants with leaves with obtuse, truncate, or subcordate bases and all major veins gently curving and parallel | |
11 Leaves with longitudinal rows of lacunae on each side of the midvein; leaves rounded at apex; seeds smooth; flowers unisexual; [subfamily Hydrilloideae] |