sy Mustard, Sisymbrium canescens.=

12b. Stems green
=Tansy Mustard, Sisymbrium canescens var. brachycarpon.=

13a. Pod short, not more than 3 times as long as wide (coarse plants,
preferring wet or sandy ground; flowers in summer) (Yellow Cress)
--14.

13b. Pod elongated, more than 4 times as long as wide --17.

14a. Stems creeping, with erect or ascending branches; flowers
about 8 mm. wide =Yellow Cress, Radicula sylvestris.=

14b. Stems erect or ascending (3-10 dm. high); flowers about 4 mm.
wide --15.

15a. Pods about twice as long as the pedicels
=Yellow Cress, Radicula obtusa.=

15b. Pods about as long as the pedicels, or shorter than them --16.

16a. Plant glabrous or minutely pubescent
=Yellow Cress, Radicula palustris.=

16b. Plant hirsute =Yellow Cress, Radicula palustris var. hispida.=

17a. Petals 7 mm. long or more; pod terminating in a conspicuous beak
(coarse, weedy plants, 3-12 dm. high, blooming in summer) --18.

17b. Petals of smaller size; pod not terminating in a conspicuous beak
--24.

18a. Upper stem-leaves clasping at the base
=Rutabaga, Brassica campestris.=

18b. Upper stem-leaves not clasping --19.

19a. Pod tipped with a slender cylindrical beak whose base is much
narrower than the pod --20.

19b. Pod gradually narrowed at its tip into a stout, flattened or angled
beak --22.

20a. Leaves oblanceolate, rather regularly pinnatifid, the terminal
segment about the same size as the lateral ones
=Sand Rocket, Diplotaxis muralis.=

20b. Leaves broad, irregularly pinnatifid especially below the
middle, with a large terminal segment --21.

21a. Beak of pod 3-4 mm. long =Black Mustard, Brassica nigra.=

21b. Beak of pod 5 mm. long or more =Indian Mustard, Brassica juncea.=

22a. Leaves dentate or lobed =Charlock, Brassica arvensis.=

22b. Leaves deeply pinnatifid --23.

23a. Pod dehiscent when ripe by two valves, tipped with a flat or angled
beak =White Mustard, Brassica alba.=

23b. Pod indehiscent, with spongy cross-partitions between the seeds,
tipped with a conical beak =Wild Radish, Raphanus raphanistrum.=