1	"Cauline leaf bases not lobed or clasping"	"Rorippa tenerrima"
1	"At least some cauline leaf bases lobed or clasping"	2
2	"Inflorescence umbel-like in fruit, congested; sepals persistent"	"Rorippa subumbellata"
2	"Inflorescence elongated, not umbel-like in fruit; sepals generally deciduous"	3
3	"Plants papillate; hairs hemispheric, sac-like"	"Rorippa sinuata"
3	"Plants not papillate; glabrous or hairs cylindric"	4
4	"Fruit valves soft hairy; sepals persistent"	"Rorippa columbiae"
4	"Fruit valves glabrous; sepals deciduous"	5
5	"Fruit +- spheric, 1.2--3 mm"	6
5	"Fruit not spheric, (2)4--18 mm"	7
6	"Perennial herb; pedicel 4--15 mm; petals 3--5 mm; style 1--1.5(2) mm"	"Rorippa austriaca"
6	"Annual or biennial; pedicel 1.5--3.7(4.3); petals 0.6--1.2 mm; style 0.1--0.7(1) mm"	"Rorippa sphaerocarpa"
7	"Stem erect, unbranched at base; petals (1.5)1.8--2.5(3) mm"	8
7	"Stem erect, prostrate to decumbent, or ascending, branches generally few to several from base; petals 0.5--1.8(2) mm"	9
8	"Stem, abaxial leaf surface densely bristly"	"Rorippa palustris subsp. hispida"
8	"Stem, generally abaxial leaf surface glabrous"	"Rorippa palustris subsp. palustris"
9	"Fruit ovoid to pear-shaped; petals erect"	"Rorippa curvipes"
9	"Fruit linear to oblong; petals spreading"	"Rorippa curvisiliqua"