Mustard Family. 13 



somewhat petioled, dentate or entire, the upper sessile, entire or toothed: 

 Sowers large; pedicels short, stout; pods elongate. I. Waste places; has been 

 collected near Ames. Story county: introduced. 



SISYMBRIUM L. Mustard. Pubescent annuals or biennials, with vari- 

 ously pinnatifid Leaves, and small white or yellow flowers.' Pods elongated, 

 terete or flatfish. Seeds oblong-, in 1-2 rows. 



S. officinale! L.) Scop. Hedge M. Stem 1-3 feet high, erect, slender. 

 mostly simple: leaves runcinate-pinnatifid, the lobes crenate, dentate, or 

 nearly entire: pods small, pointed, appressed to the stem, constricted, nearly 

 sessile. Waste places; May-September: common. 



S. canescens Nutt. Whole plant densely canescent: stem 1-:.' feet high, 

 branched: leaves twice pinnatifid, divisions small, toothed or entire, obtuse: 

 pods shorter than their horizontal slender pedicels, in long open racemes, 

 oblong, linear, or club-shaped; seeds in '.! rows in each cell. Rocky or dry 

 soil: May-July; rather frequent and wicely distributed. (Sophia pinnate 

 (Walt.) Britton.) 



S. sophia L. Similar to the preceeding: pods slender, ascending: seeds in 

 1 row in each cell. Reported from Scott county. [Sophia sophia (L.) Britton.) 



S. altissimum L. Tumbling M. Stem erect. :!—i feet high, branched, 

 glabrous: lower leaves petioled, runcinate-pinnatifid, the upper leaves short 

 petioled. pinnatifid. the segments linear or lanceolate, dentate or entire, the 

 uppermost leaves linear, bract-like: flowers yellowish: pedicels short, spread- 

 ing: pods narrowly linear. 3-4 inches long. Waste places along the railway: 

 dune-September: infrequent; Allamakee, Clayton, Dubuque, Scott, Clay, and 

 Story counties. 



Th|E»-YPOD!UM Endl. A glabrous perennial herb, with root leaves and 

 lower ones lyrate-pinnatifid, the stem leaves ovate or ovate-lanceolate, taper- 

 ing both ways, sessile, auricled, or the lower short-petioled, sharply and some- 

 times doubly toothed, and large purplish flowers. Pods terete, an inch long, 

 on short divergent pedicels; valves nerveless. Seeds in one row, oblong, mar- 

 ginless. 



T. pinnatifidum Watson. Stem 1-3 feet high. Frequent in low woods; 

 May-June: Winneshiek. Fayette. Muscatine, Johnson, Story, and Cerro 

 Gordo counties. (Iodanthus pinnatifidus ( Mx.) Steud.) 



BRASSICA L. Mustard. Introduced weeds, annual or biennial, with oppo- 

 site, incised or lyrate-pinnatifid leaves, and racemose yellow flowers. Pods 

 linear and nearly terete or 4-sided, with a long 1 -seeded beak, valves 1-.") 

 nerved. Seeds in 1 row in each cell. Style persistent. Fields and waste 

 places. 



B. nigra (L.i Koch. Black M. Stem 2-6 feet high, erect, branched: lower 

 leaves long-petioled. with a large terminal lobe and 2 or more lateral ones, 

 dentate, somewhat spiny pubescent; flowers in a large terminal raceme: 

 pod> slender, appressed. June— August; very common. 



B. sinapistrum Boiss. Wild .if. English Chariot. Leaves similar to the 

 preceeding but less pinnatifid. upper leaves scarcely toothed: pods knotted, 

 armed with a long 2-edged beak; valves strongly 1-nerved. May-September: 

 frequent. (II. arvensis (L.) B. s. P.) 



B. a I be Boiss. White M. Lower leaves obovate, deeply pinnatifid. the 

 upper lanceolate or oblong, dentate: pods bristly, ascending, beak sword- 

 shaped, as long as the pod, 1-seeded. Bather rare: reported from Muscatine, 

 Story, and Decatur counties. (Slnapsis allxi L.) 



