68 American Midland Naturalist Monograph No. 7 



18. Cruciferae B.Juss. — Mustard Family 



1. Petals yellow, yellowish, or cream (sometimes fading whitish). 

 2. Pods several times longer than wide. 



3. Pubescence of simple hairs or plants glabrous. 

 4. Pods with a distinct beak. 



5. Seeds in a single row in each locule : pods terete or slightly 

 angular. 

 6. Racemes leafy-bracted ; leaves pinnatifid with obtuse lobes; 



seeds oval 4. Erucastrum 



6. Racemes bractless; seeds subglobose 5. Brassica 



5. Seeds more or less in two rows in each locule; leaves mostly basal, 

 oblanceolate, sinuate-dentate or pinnatifid; pods flattened, 2.5- 



4 cm long, 2 mm wide 6. Diplotaxis 



4. Pods merely tipped with the style or stigma. 

 7. Leaves lobed to pinnatifid; petals yellow. 



8. Pods 4-angled; seeds in 1 row in each locule; valves of the pod 



1 -nerved 7. Barbarea 



8. Pods terete or nearly so. 



9. Valves nerveless; seeds in 2 rows in each locule 8. Rorippa 



9. Valves of the pod with \-?) nerves; seeds in 1 row in each 



locule 9. Sisymbrium 



1 . Leaves entire, cordate-clasping the stem, glabrous, glaucous; 

 petals cream, 8-10 mm long; pods linear, ascending, 8-10 cm 



long 1 1. Conringia 



3. Pubescence (at least of the leaves) of branched hairs. 



10. Leaves entire to dentate; pubescence of appressed, 2-branched 

 hairs which appear as if attached by the middle; petals more 



than 3 mm long; pods 4-angled 13. Erysimum 



10. Leaves bipinnatifid or tripinnatifid, usually finely dissected, sparse- 

 ly pubescent with short, branched hairs; petals 2-3 mm long; 



pods terete or nearly so 14. Descurainia 



2. Pods short, not more than three times as long as wide. 



11. Pods flattened parallel to the broad septum, orbicular, 3 mm broad, 

 shallowly notched at the apex; leaves linear-spatulate, entire, 



densely stellate-canescent 24. Alyssum 



1 1 . Pods turgid, not compressed, or only slightly so, ellipsoid, obovoid, 

 or globose. 



12. Leaves pinnately parted or lobed; pods ellipsoid 8. Rorippa 



12. Leav'es entire or toothed, and except in Lesquerella, sagittate- 

 clasping the stem. 



13. Pods globose 27. Lesquerella 



13. Pods obovoid 28. Camelina 



1. Petals white, pink, or purple (rarely absent), never yellow. 

 14. Pods sev^eral times longer than wide (a silique). 



15. Pods indehiscent, cylindrical, several-seeded, with pith between the 

 seeds but no true partitions, breaking at maturity into 1 -seeded 

 segments; petals purple or white. 

 16. Upper part of fruit thicker and longer than lower. 



17. Pods 2-seeded, 2-jointed 1. Cakile 



17. Pods several-seeded, several-jointed 2. Raphanus 



16. Upper part of fruit consisting of a flattened beak 3. Eruca 



15. Pods dehiscent by 2 valves, without transverse partitions. 

 18. Pods more or less flattened parallel to the septum. 



