m-aquaticum.=

34b. Aerial leaves merely serrate to pinnatifid; the submerged
leaves, if present, dissected
=Lake Cress, Radicula aquatica.=

35a. Flowers 5 mm. broad, or less --36.

35b. Flowers 6 mm. broad, or more --39.

36a. Stem-leaves irregularly pinnatifid or lobed; pod about as
broad as long (2-4 dm. high; flowers in summer)
=Garden Cress, Lepidium sativum.=

36b. Stem-leaves distinctly pinnatifid, with 3-6 pairs of lateral
segments (spring) (Bitter Cress) --37.

37a. Leaves chiefly basal, pubescent on the upper side (1-3 dm. tall)
=Bitter Cress, Cardamine hirsuta.=

37b. Stem-leaves conspicuous, glabrous on the upper side --38.

38a. Plant of dry soil; flowers about 3 mm. wide (1-4 dm. high)
=Bitter Cress, Cardamine parviflora.=

38b. Plant of moist or wet soil; flowers about 5 mm. wide (2-8 dm.
high) =Bitter Cress, Cardamine pennsylvanica.=

39a. Leaves irregularly pinnatifid or lobed, not segmented into
definitely paired divisions (coarse plants 4-8 dm. high; flowers
in summer) --40.

39b. Leaves deeply segmented into 3-10 pairs of divisions --41.

40a. Flowers pink or white from the first
=Radish, Raphanus sativus.=

40b. Flowers yellow at first, turning white with age
=Wild Radish, Raphanus raphanistrum.=

41a. Flowers pink or white, appearing in spring (2-5 dm. high)
=Cuckoo Flower, Cardamine pratensis.=

41b. Flowers yellowish or cream-color; a weed blooming in summer (5-10
dm. high) =Sisymbrium, Sisymbrium altissimum.=

42a. A fleshy, much-branched plant of the shores of the Great
Lakes, with a pod transversely divided into two joints
(2-3 dm. high; summer) =Sea Rocket, Cakile edentula.=

42b. Pod not transversely divided into two joints --43.

43a. Pod short, its length not more than 3 times its diameter --44.

43b. Pod long and slender, its length more than 3 times its diameter
--55.

44a. Pods not conspicuously flattened, thick and plump, about
circular in cross-section (flowers in summer) --45.

44b. Pods distinctly flat --46.