5. Primula L.

Plants perennial herbs, with rhizomes. Aerial stems absent. Leaves all basal, in a dense rosette, with a winged, sometimes indistinct petiole. Leaf blades simple, lanceolate to ovate, oblong-ovate, or narrowly to broadly oblanceolate, the margins entire or shallowly toothed or scalloped. Inflorescences solitary, a simple umbel terminal on a scape, this erect or ascending, unbranched, glabrous or hairy. Calyces 5-lobed, the lobes lanceolate to triangular-lanceolate, angled to sharply pointed tips. Corollas shallowly or very deeply 5-lobed, the lobes spreading or strongly reflexed, variously colored. Stamens 5, inserted on the corolla tube, the filaments short, separate or united into a tube by a membrane, the anthers exserted and united around the style or not exserted and not united in P. veris. Ovary ovoid, the style slender, extended past the anthers (except in some flowers of P. veris), the stigma capitate. Capsule ellipsoid to ovoid, 1-celled, walls thin or thick, dehiscent incompletely longitudinally from the tip into 5 valves. Seeds numerous, in our species oblong-ellipsoid to cuboid or more or less wedge-shaped, the surface with a fine to coarse network of ridges and pits. About 430 species, nearly worldwide, most diverse in temperate and montane-tropical regions

In recent studies in molecular systematics (Mast et al., 2001, 2004), Dodecatheon L. (about 17 species from North America and Siberia) is placed in a lineage that lies entirely within the much larger genus Primula (Mast and Reveal, 2007). Dodecatheon differs from Primula in its reflexed petals, united filaments, thickened connectives, and distinctive anthers. The production of heterostylous flowers is common in Primula, but apparently has been lost in Dodecatheon.

The flowers of Primula sect. Dodecatheon (L.) Mast & Reveal are fragrant, but produce no nectar. The flowers are pollinated by bumblebees (Bombus spp.). The bees hang from the anther cone and buzz their wings to release the pollen, which they collect and transfer to other flowers. Exclusion studies indicate that self-fertilization does not occur, and that the plants are dependent on bees for pollen transport (Macior, 1970b; Mast et al., 2004).