142 American Midland Naturalist Monograph No. 2 



4. Mature pods spreading or ascending, 1.5-2 mm. wide, flat; seeds 

 winged, in two rows; petals 5-8 mm. long, pink; river banks, rare. 

 Dixon, Lee Co., Vasey. June-July. [A. drummondii of auth., not 



Gray; A. divaricarpa of auth., not A. Nels.} A. confinis Wats. 



1. Pods divaricately spreading, or arcuate-recurved or pendulous at maturity. 

 6. Leaves not auricled at base, lanceolate or oblong-lanceolate, 3-12 cm. 

 long; pods pendulous, falcate, 5-7 cm. long, 2-3 mm. wide; seeds 

 winged; petals 5-6 mm. long, greenish white; sepals pilosulous; wooded 



slopes. May-July. Sicklepod A. canadensis L. 



6. Leaves, at least the median and lower, auriculate at base; mature pods less 

 than 2 mm. wide. 

 7. Mature pods 2-2.5 cm. long, straight, spreading; seeds wingless; petals 

 white or pale lavender, 2-3 mm. long; stem-leaves oblanceolate, ob- 

 tusish, unequally dentate; moist woods near streams, common. May- 

 June A. dentata T. & G. 



7. Mature pods 4-9 cm. long, arcuate-recurved; seeds winged; petals green- 

 ish white, 4-6 mm. long; plant glabrous throughout; gravelly soil in 

 woods. Apr. -June. Smooth Rockcress A. laevigata (Muhl.) Poir. 



17. Arabidopsis Heynh. 



(Sienophragma Celak.) 

 A. thaliana (L.) Heynh. Mouse-ear Cress. Waste places, nat. from Eur. 

 Apr. -June. \_Arabis thaliana L.; Sisymbrium thalianiim (L.) J. Gay] 



18. Nasturtium R. Br. — Watercress 

 N. officinale R. Br. In clear water, especially in or near springs; nat. from 

 Eurasia. May-Sept. [Sisymbriu7n nasturtium-aquaticum L.; Radicida nasturtium- 

 aquaticum (L.) Britten & Rendle} 



19. Neobeckia Greene 



N. aquatica (Eaton) Greene. Ditches, ponds, or slow streams. June- Aug. 

 \_Rorippa americana (Gray) Britt.; Radicida aquatica (Eaton) B. L. Robins.; 

 Rorippa aquatica (Eaton) Palmer & Steyerm.; Nasturtium lacustre Gray; Ar- 

 moracia aquatica (Eaton) Wieg.} 



20. Armoracia Gaertn. — Horseradish 

 A. rusticana Gaertn. Waste places, ditches, roadsides, escaped from cult.; 

 native of Eur. May-June. 



21. Alyssum L. — Sweet Alyssum 



A. alyssoides L. Fields and waste places, nat. from Eur. May-June. 



22. Berteroa DC. 



B. incana (L.) DC. Hoary Alyssum. Occasionally found in waste places, 

 adv. from Eur. June-Sept. 



23. Neslia Desv. 

 N. paniculata (L.) Desv. Ball Mustard. Waste ground, occasional; adv. 

 from Eur. May-Sept. 



