d petals each 4, stamens 6, 4 long
and 2 short (or rarely 2 only), ovary 1.

1a. Petals yellow or yellowish --2.

1b. Petals white, pink, or purple, never yellow --29.

2a. Leaves simple, entire or dentate, never lobed --3.

2b. Leaves deeply lobed or compound (the bracteal leaves, at or
near the flower-clusters, may be simple and unlobed) --10.

3a. Leaves clasping the stem --4.

3b. Leaves not clasping at base --6.

4a. Clasping base and apex of leaf obtuse or rounded; pod very long
and slender (3-8 dm. high; summer)
=Hare's Ear, Conringia orientalis.=

4b. Clasping base and apex of leaf acute; pod obovoid (3-7 dm.
high; early summer) (False Flax) --5.

5a. Stem and leaves glabrous =False Flax, Camelina sativa.=

5b. Leaves and usually the stem pubescent
=False Flax, Camelina microcarpa.=

6a. Flowers about 2 mm. wide (1-3 dm. high; flowers in summer) --7.

6b. Flowers 5 mm. wide or more (2-6 dm. high; flowers in summer)
--8.

7a. Leaves about twice as long as broad, widest near or below the middle
=Whitlow Grass, Draba nemorosa.=

7b. Leaves 3-5 times as long as broad, widest above the middle
=Yellow Alyssum, Alyssum alyssoides.=

8a. Leaves lanceolate, gradually tapering to the base; flowers
about 15 mm. wide =Sand Rocket, Diplotaxis muralis.=

8b. Leaves ovate, acute at base; flowers about 15 mm. wide --22a.

8c. Leaves entire or minutely toothed; flowers 5-10 mm. wide --9.

9a. Pods 25 mm. long or less, on slender pedicels about 8 mm. long
=Worm-seed Mustard, Erysimum cheiranthoides.=

9b. Pods 20 mm. long or more, on stout pedicels about 4 mm. long
=Worm-seed Mustard, Erysimum parviflorum.=

10a. Leaves bipinnate or dissected into very numerous divisions
(3-8 dm. high; flowers in summer) --11.

10b. Leaves simply pinnate --13.

11a. Flowers about 5 mm. broad; pods about 20 mm. long by 1 mm. broad
=Herb Sophia, Sisymbrium sophia.=

11b. Flowers about 3 mm. broad; pods about 8 mm. long by 2 mm. wide
(Tansy Mustard) --12.

12a. Stems gray with a close fine pubescence
=Tan