24a. Terminal segment of the principal leaves much larger than the
lateral segments; flowers in spring and summer --25.

24b. Terminal segment of the principal leaves equaling or smaller
than the lateral ones (5-10 dm. high; pods very long and
slender; flowers in summer)
=Sisymbrium, Sisymbrium altissimum.=

25a. Flowers about 3 mm. wide; pods erect and closely appressed to the
stem (3-9 dm. high; weed blooming in summer) (Hedge Mustard) --26.

25b. Flowers about 7 mm. wide; pods spreading or ascending (3-6 dm.
high; flowers in spring) (Winter Cress) --27.

26a. Pods pubescent =Hedge Mustard, Sisymbrium officinale.=

26b. Pods glabrous
=Hedge Mustard, Sisymbrium officinale var. leiocarpum.=

27a. Lateral leaf-segments 5-8 pairs on the principal leaves
=Winter Cress, Barbarea verna.=

27b. Lateral leaf-segments 1-4 pairs on the principal leaves --28.

28a. Flowers bright yellow, in racemes; pods spreading or ascending
=Winter Cress, Barbarea vulgaris.=

28b. Flowers pale yellow, in corymb-like clusters; pods erect and
somewhat appressed =Winter Cress, Barbarea stricta.=

29a. Principal stem-leaves compound or deeply lobed (the uppermost or
bracteal leaves may be simple) --30.

29b. Principal stem-leaves entire, dentate, serrate, or sometimes
shallowly lobed or none (the basal leaves, at the surface of the
ground, may be deeply lobed or compound) --42.

30a. Leaves ternately divided or compound (2-5 dm. high; flowers in
spring) (Toothwort) --31.

30b. Leaves pinnately divided or compound --33.

31a. Leaf-segments lanceolate or narrowly oblong
=Toothwort, Dentaria laciniata.=

31b. Leaf-segments ovate or ovate-oblong --32.

32a. Stem-leaves 2, opposite or nearly opposite
=Toothwort, Dentaria diphylla.=

32b. Stem-leaves 2-5, alternate
=Toothwort, Dentaria maxima.=

33a. Plants growing in water, or in mud near water (spring and summer)
--34.

33b. Plants of dry or moist soil --35.

34a. Aerial leaves distinctly compound, with 3-11 leaflets
=Water Cress, Radicula nasturtiu