Annual or perennial (rarely biennial) herbs (suffrutescent in some Primula), sometimes somewhat succulent (Androsace), sometimes rhizomatous (Primula), sometimes stoloniferous (Primula), sometimes with glandular hairs producing crystalline substance that forms farinose coating (Primula); resin canals sometimes present (Hottonia). Stems sometimes inflated (Hottonia). Leaves in basal rosettes (cauline and alternate, opposite, or whorled in Hottonia), simple (pinnately compound in Hottonia); stipules absent; petiole present or absent; blade margins entire, denticulate, ciliolate, or crenulate. Inflorescences terminal, scapose or sessile umbels or solitary flowers; bracts usually present. Flowers bisexual, homostylous or heterostylous (Hottonia, Primula); perianth and androecium hypogynous; sepals 4–5, connate proximally into tube; petals 4–5, connate proximally, corolla campanulate to salverform or tubular with long or short tube; nectaries absent or sometimes nectariferous hairs present; stamens 5, antipetalous, epipetalous, distinct or connate proximally; anthers opening by longitudinal slits; staminodes absent; pistils 1, 5-carpellate; ovary superior, 1-locular; placentation free-central with ± globose central axis; ovules anatropous, bitegmic, not embedded in placentae, tenuinucellate; styles 1, terminal; stigmas 1, usually capitate (rarely truncate). Fruits capsular, dehiscence valvate or operculate. Seeds 1–200+, brown or black, angular or rounded, (rarely with eliasomes in some Primula); embryo straight; endosperm copious, starchless.
North America, Mexico, West Indies, Central America, South America, Eurasia, mainly n temperate to arctic.
Genera 20, species ca. 600 (5 genera, 52 species in the flora).
The largest genera in Primulaceae are Primula (ca. 500 species) and Androsace (ca. 100 species). No genera are endemic to the flora area; Dodecatheon and Douglasia have relatively few representatives elsewhere (northeastern Asia).
The family contains ornamental taxa, especially in Dodecatheon and Primula. Primula can cause dermatitis. Some taxa are pollinated by insects; selfing also occurs. Seeds are dispersed by gravity, water, wind, or ants (Primula; B. Ståhl and A. A. Anderberg 2004).
As typically described (e.g., A. Cronquist 1981; V. H. Heywood 1978), Primulaceae were clearly polyphyletic, closely related to Myrsinaceae and Theophrastaceae. M. Källersjö et al. (2000) and B. Ståhl and A. A. Anderberg (2004) removed the nonrosette terrestrial members from Primulaceae in the broad sense and placed them in the Myrsinaceae, which are further distinguished by leaves and calyx often dotted with yellow or dark streaks, flowers with relatively shorter corolla tubes, seeds immersed in placentae, and wood devoid of rays or with multiseriate rays only. Maesa, consisting entirely of trees found in the Eastern Hemisphere tropics, also has semi-inferior ovaries, pedicels with two bracts, and wood with both uniseriate and multiseriate rays; it, too, was removed from Primulaceae/Myrsinaceae and placed in its own family (Källersjö et al.). The families Primulaceae in the narrow sense, Myrsinaceae, Theophrastaceae (including Samolaceae), and Maesaceae then form a monophyletic clade within Ericales (P. F. Stevens, http://www.mobot.org/MOBOT/research/APweb/), sharing some features, most notably flowers with sympetalous corollas, stamens in a single series and opposite the petals, free-central placentation, bitegmic, tenuinucellate ovules, and plants generally with tannins and saponins.
Additional evidence (L. Martins et al. 2003) indicates that Androsace and Primula may not be monophyletic; more work is needed to resolve these issues. The work of M. Källersjö et al. (2000) showed that Douglasia should remain separate from Androsace, and Dodecatheon should remain separate from Primula, although Dodecatheon clearly is derived from Primula subg. Auriculastrum. Alternative views suggesting more inclusive concepts of Primula and Androsace have been offered by I. Trift et al. (2002), A. R. Mast et al. (2004), and G. M. Schneeweiss et al. (2004). The phylogenetic position of Cyclamen, a scapose taxon currently included in Myrsinaceae, has not been resolved. Our understanding of Primulaceae is still in flux, and future taxonomic realignments at the familial and generic levels are to be expected.
Källersjö, M., G. Bergqvist, and A. A. Anderberg. 2000. Generic realignment in primuloid families of the Ericales s.l. (Angiosperms): A phylogenetic analysis based on DNA sequences from three chloroplast genes and morphology. Amer. J. Bot. 87: 1325–1341.
Mast, A. R., D. M. S. Feller, S. Kelso, and E. Conti. 2004. Buzz-pollinated Dodecatheon originated from within the heterostylous Primula subgenus Auriculastrum (Primulaceae): A seven-region cpDNA phylogeny and its implications for floral evolution. Amer. J. Bot. 91: 926–942.
Schneeweiss, G. M., P. Schonswetter, S. Kelso, and H. Niklfeld. 2004. Complex biogeographic patterns in Androsace and related genera: Evidence from phylogenetic analyses of nuclear internal transcribed spacer and plastid trnL–F sequences. Syst. Biol. 53: 856–876.
|1||Leaves pinnately compound.||Hottonia|
|1||Leaves simple||> 2|
|2||Corolla lobes reflexed, lengths 2+ times tube; stamens exserted, anthers connivent.||Dodecatheon|
|2||Corolla lobes not reflexed, lengths to 2 times tube; stamens included, anthers not connivent||> 3|
|3||Sepals keeled (at least on tubes), glabrous or stellate-hairy; corollas pink, rose, or purple; plants usually perennial, cushion- or mat-forming||Douglasia|
|3||Sepals not keeled or only weakly keeled in fruit, glabrous, pilose, or puberulent; corollas lavender, magenta, pink, purple, rose, violet, white, or yellow; plants annual, biennial, or perennial, usually not cushion- or mat-forming||> 4|
|4||Corollas white, fading to pink, (usually to 5 mm, if 5+ mm, plants hairy); flowers homostylous.||Androsace|
|4||Corollas lavender, magenta, pink, purple, rose, violet, yellow, or some- times white, (7+ mm, plants never grayish-pilose); flowers heterostylous or homostylous.||Primula|