18. Cruciferae 71 



1. Upper leaves sessile and clasping by the auriculate base. 

 5. Plants glaucous, usually partly hispid when young. 



6. Roots slender: leaves not fleshy: fields and waste places; nat. 



from Eur. Apr.-Oct. Yellow Mustard B. campestris L. 



6. Roots thicker; leaves fleshy; fields and waste places; introd. 



from Eur. Cabbage B. oleracea L. 



5. Plants not glaucous; roots thickened; persisting occasionally 

 from cult. Turnip B. rapa L. 



6. Diplotaxis DC. — Sand Rocket 

 D. muralis (L.) DC. Waste places, occasional; adv. from Eur. 

 June-Aug. 



7. Barbarea R.Br. — Wintercress 



1. Petals bright yellow, 6-8 mm long; basal leaves with 2-8 lateral 

 leaflets; mature pods 1.5-2.5 cm long, the pedicel not as thick 

 as the pod; roadsides, fields, and waste places, very common; 

 nat. from Eur. Apr.-June. Common Wintercress [B. stricta 

 sensu auth., non Andrz.] B. vulgaris R.Br. 



1. Petals pale yellow, 4-6 mm long; basal leaves with 8-16 lateral 

 leaflets; mature pods 5-6 cm long; pedicels about as thick as 

 the pods; waste places; nat. from Eur. Early Wintercress [B. 

 praecox R.Br.] B. verna (Mill.) Aschers. 



8. Rorippa Scop. — Yellow Cress 

 1. Petals 3-5 mm. long; perennials with rhizomes. 



2. Leaves pinnately divided, not auriculate at base; pods linear, 

 the style 0.5 mm long; moist ground; nat. from Eur. May- 

 Sept R. sylvestris (L.) Besser 



2. Leaves pinnately lobed, auriculate at base; mature pods cylin- 



drical, the style 2-3 mm long; river banks. Apr.-Aug 



R. sinuata (Nutt.) Hitchc. 



L Petals 1-2 mm long; leaves with small auricles at ba.se; style on 

 mature pods 0.5-1 mm long; annual or biennial natixe species. 



3. Pedicels short, not more than 1-2 mm long; pods 6-10 mm long, 



ellipsoid; stem glabrous; median and upper leaves shallowly 

 toothed or sinuate; muddy creek banks, or in fields, common. 



May-Oct R. sessiliflora (Nutt.) Hitchc. 



3. Pedicels and pod usually 3-5 mm long; leaves usually pinnatifid, 



especially toward the base. 



4. Stem and leaves hirsutulous; p>ods 1-2 times as long as wide 



and slightly shorter than the pedicel, wet ground, rare; 



Cook Co., E. J. Hill, A. Chase; McHenry Co., W. A. Nason 



R. hispida (Desv.) Britt. 



4. Stem and leaves glabrous; pods about twice as long as wide, 

 and longer than the pedicels; wet ground or in water, 

 common throughout 111. May-Oct. [R. palustris (L.) 

 Besser] R. islandica (Oeder) Borbas 



