Annual, biennial or perennial herbs, similar to the Mustards, with basal and alternate pinnatifid or lobed leaves, and rather large yellow flowers in terminal racemes. Silique elongated, linear, flat or flattish, short-beaked or beakless, the valves mostly 1-nerved. Style usually slender Seeds in 2 complete or incomplete rows in each cavity of the silique, margin-ginless; cotyledons conduplicate. [Greek, referring to the double rows of seeds.]

About 20 species, natives of the Old World, the following fugitive or adventive in our territory. Type species: Diplotaxis tenuifolia (L.) DC.

1. Diplotaxis Tenuifolia (L.) Dc. Wall Rocket

Fig. 2108

Sisymbrium tenuifolium L. Cent. Pl. 1: 18. 1755. Diplotaxis tenuifolia DC. Syst. 2: 632. 1821.

Perennial, glabrous or nearly so, somewhat glaucous, stem branched, bushy, leafy, 1°-4° high. Leaves pinnatifid, often nearly to the midrib, thin, the lower 3'-6' long, the lobes distant or close together, mostly narrow; racemes elongated in fruit, loose; flowers 8"-10" broad; pods 1'-1 1/4' long, about 1 1/4" wide, nearly erect; pedicels slender, 10"-20" long in fruit.

In waste places and ballast, Nova Scotia to Ontario, New Jersey and Pennsylvania, chiefly about the cities and in California. Adventive from Europe. Cross-weed. June-Aug.

2. Diplotaxis Muralis (L.) Dc. Sand Rocket

Fig. 2109

Sisymbrium murale L. Sp. Pl. 658. 1753. Diplotaxis muralis DC. Syst. 2: 634. 1821.

Annual, branched from the base, sparingly hispid or glabrous, the slender branches 1°-2° high, leafy only below. Leaves oblanceolate, sinuate-lobed or sometimes pinnatifid, 2'-4' long, narrowed at the base, mostly slender-petioled; fruiting racemes long, loose; flowers 6"-8" broad; pod abort 1' long and 1" wide, erect, flattish; fruiting pedicels 4"-8" long.

In waste places and ballast, Nova Scotia to Pennsylvania and in Bermuda. Adventive from Europe. Flix- or cross-weed. June-Aug.