Woad [Greek isatis, name used for a dye plant, most likely woad]

Ihsan A. Al-Shehbaz

Biennials [annuals, perennials]; not scapose; (often glaucous), glabrous or pubescent. Stems erect, often unbranched basally, paniculately branched distally. Leaves basal and cauline; petiolate or sessile; basal rosulate [or not rosulate], petiolate [rarely sessile], blade margins entire, repand, or dentate [rarely pinnately lobed]; cauline blade (base auriculate, sagittate, [or amplexicaul, rarely attenuate]), margins entire [dentate]. Racemes (corymbose, in panicles, several-flowered), considerably elongated in fruit. Fruiting pedicels reflexed, slender, (filiform, often thickened and clavate apically). Flowers: sepals erect or ascending, oblong [ovate]; petals oblanceolate [obovate, spatulate, or oblong], (equal to or longer than sepals), claw absent, (apex obtuse [subemarginate]); stamens slightly tetradynamous; filaments not dilated basally; anthers oblong [ovate], (apex obtuse or apiculate); nectar glands (6) confluent, or (4) lateral and median. Fruits siliques or silicles (samaroid), sessile, oblong, oblanceolate, elliptic, or obovate [ovate, cordate, spatulate, orbicular], 1- (or 2-)seeded, smooth, strongly angustiseptate, (prominently winged all around or distally; seed-bearing locule papery or corky, distinctly or obscurely 1-3-veined, sometimes keeled or shortly winged), glabrous or pubescent; valves and replum united; septum absent; ovules 1 (or 2) per ovary, (subapical); stigma capitate. Seeds plump, not winged, narrowly oblong; seed coat (smooth), not mucilaginous when wetted; cotyledons incumbent or accumbent.

Species 50 (1 in the flora): introduced; Europe, c, sw Asia, n Africa; introduced also in South America (Chile, Peru).

Lower Taxon

• Isatis tinctoria Linnaeus