45a. A plant escaped from cultivation in dry or moist soil, with very
large basal leaves (5-10 dm. high)
=Horse Radish, Radicula armoracia.=

45b. A plant of water or very wet soil, the largest leaves seldom more
than 15 cm. long (1-5 dm. tall) =Lake Cress, Radicula aquatica.=

46a. Stem-leaves clasping the stem by an auricled base --47.

46b. Stem-leaves sessile or petioled, not clasping, or none --49.

47a. Stem and leaves glabrous or pubescent; pod very flat and circular,
about 10 mm. wide (1-5 dm. tall; early summer)
=Penny Cress, Thlaspi arvense.=

47b. Stem and leaves glabrous or pubescent; pod not more than 5 mm. wide
(1-6 dm. high; spring and early summer) --48.

48a. Pods broadly ovate =Field Cress, Lepidium campestre.=

48b. Pods triangular, or slightly indented at the apex
=Shepherd's Purse, Capsella bursa-pastoris.=

49a. Pods about circular, or a very little longer than broad --50.

49b. Pods ovoid or oblong, broadest near the middle, and distinctly
longer than wide (Whitlow Grass) --53.

50a. Leaves entire (1-3 dm. high; flowers in summer)
=Yellow Alyssum, Alyssum alyssoides.=

50b. Leaves serrate (2-6 dm. high; flowers in summer) --51.

51a. Stamens 6 =Garden Cress, Lepidium sativum.=

51b. Stamens 2 (Pepper Grass) --52.

52a. Petals present =Pepper Grass, Lepidium virginicum.=

52b. Petals none =Pepper Grass, Lepidium apetalum.=

53a. Petals deeply 2-cleft (about 1 dm. high; early spring)
=Whitlow Grass, Draba verna.=

53b. Petals entire or barely notched at the tip --54.

54a. Leaves all or chiefly at or near the base (about 1 dm. high;
spring) =Whitlow Grass, Draba caroliniana.=

54b. Stems leafy up to the flowers (1-5 dm. high; summer)
=Whitlow Grass, Draba arabisans.=

55a. Stem-leaves cordate or sagittate at the base and sessile, forming a
more or less clasping leaf (3-10 dm. high) (Rock Cress) --56.

55b. Stem-leaves sessile or somewhat petioled, but not clasping --63.

56a. Seeds in 2 rows in each cavity of the pod (early summer) --57.

56b. Seeds in 1 row in each cavity of th