Isatis L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1964, Flora Europaea - Volume 1. Lycopodiaceae to Platanaceae, Cambridge University Press : 268-269

14. Isatis L. 1

Annual to perennial, glaucous herbs; glabrous or with unbranched hairs. Cauline leaves simple, entire, usually amplexicaul. Sepals not saccate; petals yellow, shortly clawed. Fruit an indéhiscent, 1-seeded silicula with a wide, often inflated, wing surrounding the loculus; loculus usually with a distinct longitudinal rib; stigma sessile.

A difficult genus urgently requiring revision. Species 4-9 are all very similar and some are probably better regarded as subspecies of 7.

1 Cauline leaves attenuate at base, not amplexicaul 3. sabulosa

1 Cauline leaves amplexicaul

2 Silicula orbicular-elliptical, not more than twice as long as wide, rounded at base and apex or emarginate at apex

3 Perennial; cauline leaves cordate at base; silicula 15-25 mm 1. allionii

3 Annual; cauline leaves sagittate at base; silicula 8-1 0mm 2. platyloba

2 Siliculaat least twiceaslongaswide, attenuateat baseorapex, or at both

4 Annual; silicula 6-8 times as long as wide 10. lusitanica

4 Biennial or perennial; silicula 2-5 times as long as wide

5 Central rib of silicula conspicuously 3-ridged 5. costata

5 Central rib of silicula simple

6 Silicula 2-3 times as long as wide 7 Central rib of silicula very wide 4. laevigata 7 Central rib of silicula slender (cf. also 7) 6. praecox

6 Silicula mostly at least 3 times as long as wide 8 Silicula 5-8 mm wide, oblong; cauline leaves with obtuse auricles (Turkey) 9. arenaria 8 Silicula elliptical, obovate or oblanceolate, usually narrower; caulineleaves with acute auricles 9 Biennial without vegetative shoots; flowering stems usually at least 50 cm (widespread) 7. tinctoria 9 Perennial with vegetative shoots at base; flowering stems 20-40 cm (Athos) 8. athoa