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 Stigmas 2-branched; fruits truncate at apex, obpyramidal, very abruptly beaked, 4-8 (-10) mm broad; [subgenus Sparganium] | |
2 Leaves and inflorescence primarily emergent, with few or no leaves floating on water surfaces; leaves keeled throughout or at least basally. | |
3 Rachis of inflorescence unbranched; fruit beak straight to curved; tepals reaching about half the length of fruit body; leaves often keeled distally; perianth segments essentially translucent and lacking an apical dark spot | |
3 Rachis of inflorescence branched; fruit beak curved; tepals reaching about half or more the length of fruit body; leaves usually keeled only near bases (S. americanum) or from base to at least the middle of leaves (S. androcladum(); perianth segments not translucent, their apices with a dark brown or black pad of tissue. | |
4 Mature fruits dull, finely pitted, the body 3-5 mm long; fruiting heads 1.5-2.5 cm in diameter; branches of the inflorescence with (0-) 1-3 pistillate heads (in addition to staminate heads); stigma 0.8-1.9 (-2.8 in the Coastal Plain) mm long; leaves erect but not stiffened | |
4 Mature fruits shiny, smooth, the body 5.5-7 mm long; fruiting heads 2.5-3.5 cm in diameter; branches of the inflorescence with 0 (-1) pistillate heads (in addition to staminate heads); stigma 1.5-3 mm long; leaves stiff | |
2 Leaves and inflorescence primarily floating, limp on the surface of water (sometimes with a few emergent stems); floating leaves usually without keels and mostly flattened or usually at least basally keeled (as in S. acaule). | |
5 Rachis of inflorescence unbranched, either floating, the distal portion erect at water surface, or completely erect on entirely emergent plants. | |
6 Staminate heads 1; pistillate heads borne directly in axils of leaves or bracts; beak of fruit 0.5-1.5 mm long | |
6 Staminate heads 2 or more; pistillate heads (some or all) borne above the axils of leaves or bracts; beak of fruit 1.5-4.3 mm long | |