72 American Midland Naturalist Monograph No. 7 



9. Sisymbrium L. 



1. Pods 1-1.5 cm long, on very short pedicels closely appressed to the 



stem; petals 3 mm long; stem divaricately branched above; 



leaves pinnatifid into 5-13 lobes; waste ground, common; nat. 



from Eur. May-Sept. Hedge Mustard S. officinale (L.) Scop. 



1. Pods 3-10 cm long, spreading or ascending on slender pedicels; 



petals 5-8 mm long. 



2. Lower part of stem spreading-hirsute ; upper leaves with linear 

 divisions; petals pale yellow, 6-8 mm long; pods 7-10 cm long, 

 the ascending pedicels 5-8 mm long; a common weed in fields 

 and waste places; nat. from Eur. May- Aug. Tumble 

 Mustard S. altissimum L. 



2. Lower part of the stem retrorsely hirsute; upper leaves with 

 lanceolate divisions; petals bright yellow, 5-6 mm long; pods 

 3 cm long, on spreading pedicels 1-1.5 cm long; fields and 

 waste places; adv. from Eur. May-Nov S. loeselii L. 



10. Alliaria B.Ehrh. — Garlic Mustard 



A. officinalis Andrz. Roadsides, waste places, and in woods; nat. 

 from Eui'.; known to occur in Carroll, Piatt, Sangamon, Tazewell, and 

 Winnebago counties. May- June. 



11. Conringia Adans. — Hare's-ear Mustard 



C. orient alis (L.) Dum. Waste places, occasional; adv. from Eur. 

 May-July. 



12. Hesperis L. — Rocket 

 H. matronalis L. Roadsides, waste places, cultivated ground; 

 escaped from cult. ; introd. from Eur. June-July. 



13. Erysimum L. 



1. Petals 1.5-2 cm long; pods 4-8 cm long, 2 mm thick; sandy soil; 



Cass, Fulton, Hancock, La Salle, Mason, and Menard counties. 



May-June. Western Wallflower [E. arkajisanurn Nutt.] 



E. asperum (Nutt.) DC. 



1. Petals 4-8 mm long. 



2. Fruiting pedicels 3-8 mm long; petals 6-8 mm long. 



3. Pods 6-8 cin long, divaricately spreading; leaves mostly 

 repand-dentate or denticulate; waste places, roadsides, or 

 fields; adv. from Eur. Apr. -June E. repandum L. 



3. Pods 3.5-4.5 cm long, nearly erect; leaves entire; dry ground, 

 not common; chiefly in the northern half of 111. [E. parvi- 

 florujn Nutt., non Pers.] E. inconspicuum (Wats.) MacM. 



2. Fruiting pedicels slender, 1 cm long; pods ascending, 1.5-2.5 cm 

 long, 1-1.5 mm wide; petals 4-5 mm long; leaves entire or 

 nearly so; fields and waste places; chiefly in the n. half of the 

 state. June-Aug. Wonnseed Mustard E. cheiranthoides L. 



