Prunella L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1972, Flora Europaea. Volume 3. Diapensiacea to Myoporaceae, Cambridge: Cambridge University Press : 162

21. Prunella L. 1

Perennial herbs. Verticillasters mostly 6-flowered, in dense, terminal, cylindrical spikes; bracts distinctly different from the leaves; bracteoles small or absent. Calyx tubular-campanulate, 2-lipped, closed in fruit; upper lip more or less 3-toothed; lower lip with 2 larger teeth. Corolla-tube exceeding calyx, straight, obconical, with a ring ofhairs inside; upper lip distinctly hooded; lower lip denticulate. Filaments with a subulate appendage below the apex; anther-cells divergent. Nutlets oblong.

All four species are interfertile, and consequently hybrids are common where two or more of them grow together. There is a complete range of intermediates between the extremes of the different species in respect of nearly every character, and all of this variation may be due to hybridization.

1 Corolla usually more than 18 mm; inflorescence not subtended by leaves 2. grandiflora 1 Corolla not more than 17 mm; inflorescence usually subtended by leaves

2 Corollayellowish-white,rarelypinkorpurplish; at least the upper leaves pinnatifid or lobed; teeth of lower lip of calyx linear-lanceolate 1. laciniata 2 Corollaviolet,rarelywhite; leavesentireorcrenulate; teeth of lower lip of calyx lanceolate

3 Leaves ovate to rhombic-ovate, entire or crenulate, petiolate; middle tooth of upper lip of calyx wider than lateral teeth

3. vulgaris 3 Leaves linear-lanceolate to elliptic-lanceolate, entire, sessile; teeth of upper lip of calyx subequal 4. hyssopifolia