16.
Rorippa sessiliflora
(Nuttall) Hitchcock, Key Spring Fl. Manhattan. 18. 1894. (as Roripa).
Nasturtium sessiliflorum
Nuttall in J. Torrey and A. Gray, Fl. N. Amer. 1: 73. 1838;
N. limosum
Nuttall;
Radicula limosa
(Nuttall) Greene;
R. sessiliflora
(Nuttall) Greene
Annuals;
glabrous throughout.
Stems
(simple or several-branched from base) erect, branched distally, (0.9-) 2-4.5(-6.3) dm.
Basal leaves
not rosulate; blade margins dentate.
Cauline leaves
shortly petiolate or sessile; blade oblong or oblanceolate to obovate, 1.5-7(-13.3) cm × (5-)10-28(-50) mm, (lateral lobes much smaller than terminal), base auriculate or not, margins dentate or less frequently sinuate, or (lateral lobes) denticulate or entire.
Racemes
considerably elongated.
Fruiting pedicels
divaricate-ascending to horizontal, straight, 0.5-2(-4) mm, (slender or stout).
Flowers:
sepals ascending to spreading, ovate, 1.2-2 × 0.5-0.8 mm; petals absent; median filaments 1-1.6 mm; anthers ovate, 0.2-0.3 mm.
Fruits
siliques, straight or curved, oblong to oblong-linear, (4-)6-9(-12) × (1.4-)1.8-2.8(-3.5) mm; ovules 158-242 per ovary; style 0.1-0.5 mm.
Seeds
biseriate, yellow-brown, cordiform, 0.4-0.5 mm, foveolate.
2
n
= 16.
Flowering Mar-Oct. Mud flats, ditches, wet old fields, roadsides, sloughs, fallow fields, floodplains, stream banks, edges of pools, waste grounds, gardens; 0-300 m; Ala., Ark., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Mass., Miss., Mo., Nebr., N.C., Ohio, Okla., S.C., S.Dak., Tenn., Tex., Va., Wis.
Both R. L. Stuckey (1972) and R. C. Rollins (1993) indicated that
Rorippa sessiliflora
has strongly saccate sepals, but all specimens that I examined failed to show any sign of this character. The species is very distinctive and can easily be distinguished by an absence of petals and by having fruiting pedicels 0.5-2(-4) mm.
