12 CRUCIFERAE. 



Wet places; April July; infrequent; Clinton. Muscatine, Story, Van Buren. 

 Decatur, and Page counties, i R. sessillflora ( Nutt.) A. s. II.) 



N. obtusum Nutt. Stem much branched, diffusely spreading: leaves 

 pinnately parted or divided: flowers very small on short pedicels: pods longer 

 than tlu- pedicels, varying from linear-oblong to short-oval. Moist places: 

 April-August; infrequent: Scott. Johnson, and Decatur counties. ( B, obtusa 

 i Nut,. i Britt.) 



* * Perennial; flowers it>hH<' <>r yellow, usually large and shout/; leaves undi- 

 vided nr pinnatifid. 



I Flowers white. 



N. armoracia ( L.) Fries. Horseradish. Stem erect. 2-3 feet high, from a 

 la roe descending root: root-leaves long-petioled. very large, oblong, crenate. 

 sinuate or sometimes pinnatifid: cauline leaves oblong-ovate to lanceolate, 

 sessile, dentate or crenate: pods globular, or oblong, pedicels erect, many 

 times longer than the pod: style short. Frequently found near old building 

 sites and about gardens: May-June: infrequent: fruit rarely found. ( It. 

 armoracia (L.) A. S. H.) 



N. lacustre Gray. Lake Cress. Aquatic: stem 1-2 feet long, branched, 

 immersed leaves dissected into many filiform divisions, emerscd leaves 

 oblong, obtuse or acute, entire, serrate, lobed, or pinnatifid: pedicels slender. 

 widely spreading; petals longer than the sepals; pods ovoid, 1-celled. Pcuds 

 and streams: July-August: infrequent: local. Clinton and Muscatine coun- 

 ties. ( R. americana (Gray) Britton.) 



IN. officinale R. Br. True W. C. Stem spreading, rooting: leaves pinnate: 

 leaflets 3-11, nearly entire, rounded to oblong; petals twice the length of the 

 calyx: pods linear, about an inch long, pedicels slender, widely divergent. 

 In water or wet places; April-August; rather rare: Winneshiek. Fayette, 

 Story, and Page counties. 



f f Flowers yellow. 



N. sinuatum Nutt. Plant low, decumbent, some brauched: leaves oblong, 

 pinnatel}' cleft, divisions linear or oblong, entire or sparingly dentate: pods 

 linear-oblong, slightly curved, slender pedicelled: styles slender. Mississippi 

 and Missouri river bottoms; June-September: common: Scott, Henry. Page, 

 Pottawattomie, and Fremont counties. (R. slnuata (Xutt.) A. S. II.) 



BAPBAI^EA P. Br. Winter Cress. Pods linear-terete, obscurely 4-sided; 

 seeds marginless, one row in each cell. 



B. vu'gcris R. Br. Yellow Rocket, stems tufted. ] -2 feet high: lower leaves 

 petioled. pinnatifid, the divisions oval or obovate, repand-toothed or entire. 

 the terminal division much larger than the lateral ones: cauline leaves 

 usually sessile, sometimes clasping by an auricled base, obovate, cut-toothed 

 or pinnatifid; pods half-inch long; pedicels one-third the length of the pods, 

 erect or spreading. Fields and waste places: May-June; infrequent: Jones, 

 Johnson. Story. Boone, and Shelby counties. ( Ji. barbarea { L) Mac M.) 



ERYSIMUM L. Mostly biennials, with entire, toothed, or lobed leaves, and 

 small yellow flowers. Pods 4-angled, small, linear: valves keeled by a promi- 

 nent v< in Seeds mirginless, oblong, in l row. 



E. ch^iranthoides L. Worm-seed Mustard. Stem 1-2 feet high, slender. 

 simple, erect; leaves narrowly lanceolate, entire or scarcely toothed: pods 

 about an inch Long; pedicels scarcely shorter, divergent; pod and pedicels 

 angled to each other. Woods: June-August; common. 



E. asperum D«'. Western Wall-flower. Power leaves lanceolate or linear, 



