This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Biennial herbs, with alternate pinnatifid or dentate leaves and medium-sized yellow flowers. Pubescence, when present, of simple hairs. Sepals spreading. Pods narrowly linear, much elongated, terete or nearly so, divergent or ascending. Stigma 2-lobed. Seeds in 1 or 2 rows in each cell of the pod, oblong, not winged. Cotyledons incumbent. [Name unexplained.]
About 10 species, natives of the Old World. Type species: Sisymbrium strictissimum L.
Sisymbrium altissimum L. Sp. Pl. 659. 1753. Sisymbrium Sinapistrum Crantz, Stirp. Aust. Ed. 2, 52.
1769. Sisymbrium pannonicum Jacq. Coll. 1: 70. 1786.
Erect, 2°-4° high, freely branching, glabrous or nearly so. Lowest leaves runcinate-pinnatifid, petioled, the lobes lanceolate, often auriculate; upper leaves smaller, shorter petioled or nearly sessile, very deeply pinnatifid, the lobes linear or lanceolate, dentate or entire, often with a narrow projection on the lower side near the base; uppermost leaves often reduced to linear nearly entire bracts; flowers yellowish, about 3" broad; pedicels 3"-4" long, spreading or ascending, thickened in fruit; pods very narrowly linear, stiff, divergent, 2'-4' long, 1/2" wide; valves with a prominent midrib.
Norta Irio (L.) Britton [Sisymbrium Irio L.] differs by runcinate-pinnatifid leaves, the terminal segment usually larger than the lateral ones, and soft ascending pods; it occurs occasionally in ballast and waste grounds.