Isatis L. Isatis allionii, P. W. Ball

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

1. I. allionii P. W. Ball , Feddes Reperì. 69: 57 (1964)

(/. alpina All. et auct. mult., non Vili.).

Perennial with branched rhizome and vegetative shoots; flowering stems 10-30 cm. Cauline leaves with obtuse auricles. Petals (3-)4-5 mm. Silicula 15-25 x 8-13 mm, orbicular-elliptical, sometimes subcordate at base. • S. W. Alps; N. & C. Appennini. Ga It.