43 



9a. Pods 25 mm. long or less, on slender pedicels about 8 mm. long 

 Worm-seed Mustard, Erysimum cheiranthoides. 



9b. Pod's 20 mm. long or more, on stout pedicels about 4 mm. long 



Worm-seed Mustard, Erysimum parviflorum. 



lOa. Leaves bipinnate or dissected into very numerous divisions 



(3 8 dm. high; flowers in summer) 11. 

 lOb. Leaves simply pinnate 13. 



Ha. Flowers about 5 mm. broad; pods about 20 mm. long by 1 mm. 

 broad Herb Sophia, Sisymbrium sophia. 



lib. 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 



Tansy Mustard, Sisymbrium canescens. 

 12b. Stems green 



Tansy Mustard, Sisymbrium canescens var. bracliycarpon. 



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 iar. hispida. 



17a. Petals 7 mm. long or more; pod terminating in a conspicuous 

 beak (coarse, weedy plants, 3 12 dm. high, blooming in sum- 

 mer) 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 t.out, 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. 



