Jones: Flora of Illinois, 71. Cruciferae 141 



14. loDANTHus T. &: G. 

 /. pinnatifidus (Michx.) Steud. Woods, especially near streams, common. 

 May-July. 



15. Cardamine L. — Bittercress 

 1. Leaves toothed or entire; petals 7-12 mm. long; plants perennial; stem with 

 a tuberous base. 

 2. Petals white; stem 15-50 cm. tall, puberulent at base, otherwise glabrous; 



basal leaves oval; cauline leaves 4-8; wet ground. May-June 



C. bulbosa (Schreb.) BSP. 



2. Petals pale lavender; stem 10-25 cm. tall, sparsely hirsute, varying to 



glabrous; basal leaves orbicular; cauline leaves 2-6; woods. Apr.-May .... 



C. douglassii (Torr.) Britt. 



1. Leaves pinnate or pinnatifid. 



3. Petals white or pink, 8-13 mm. long; plants perennial; wet ground, n. 



III., rare. Apr.-May C. pratensis L. 



3. Petals white, 2-3 mm. long; plants annual. 



4. Leaves nearly all basal, more or less pubescent; stamens 4; an occasional 



weed in cultivated ground; nat. from Eur. Apr.-May ....C. hirsuta L. 



4. Stem more or less leafy, the leaves glabrous; stamens usually 6; native 



plants. 



5. Leaflets or leaf -segments of the median and upper leaves oblong to 



oval, often toothed, the terminal one larger; rachis narrowly 



winged; wet soil. Apr.-Aug C. pennsylvanica Muhl. 



5. Leaflets or leaf-segments of the median and upper leaves linear, 

 entire, not decurrent, the terminal one similar; rachis not winged; 

 moist soil. Apr.-May C arenicola Britt. 



16. Arabis L. — Rockcress 

 1. Pods erect or ascending. 



2. Stem-leaves and basal leaves pinnatifid; pods ascending, 2-2.5 cm. long; 

 petals 1.5-3 mm. long; rocky woods in the s. half of 111. Apr.-May 

 [^Sibara yirginica (L.) Rollins} A. yirginica (L.) Poir. 



2. Stem-leaves entire or dentate. 



3. Stem-leaves not auricled at the base, spatulate or linear, 1-3 cm. long; 

 basal leaves pinnatifid; pods ascending, 2-3.5 cm. long; petals 6-8 mm. 



long; rocky or sandy soil in the n. third of 111. May-July 



A. lyrata L. 



3. Stem-leaves auricled at the base; basal leaves entire or dentate. 

 4. Mature pods erect or appressed, not more than 1 mm. wide. 



5. Pods 5-9 cm. long, nearly terete; seeds almost wingless, in two dis- 

 tinct rows; petals 3-4 mm. long, cream or pale yellowish; waste 

 places, nat. from Eur. May-July. [Turritis glabra L.} Tower 

 Mustard A. glabra (L.) Bernh. 



5. Pods 4-5 cm. long, flat; seeds winged, in only 1 row; petals 4-5 

 mm. long, white or pale pink; among rocks near streams. May- 

 June. [A. hirsuta Am. Auth.; A. ovata (Pursh) Poir. (?)] 



A. pycnocarpa Hopkins 



