PRIMULACEAE, in botany, an order of Gamopetalous Dicotyledons belonging to the series Primulales and containing 28 genera with about 350 species.
A gamopetalous corolla falls off in one piece; but sometimes the base of the corolla remains persistent, as in Rhinanthus and Orobanche.
When a corolla is gamopetalous it usually happens that the lower portion forms a tube, while the upper parts are either free or partially united, so as to form a common limb, the point of union of the two portions being the throat, which often exhibits a distinct constriction or dilatation.
Amongst gamopetalous plants several of our largest living families, including Campanulaceae, Labiatae, Solanaceae and Primulaceae, are still missing; and of Boragineae, Scrophularineae, Gentianeae and Caprifoliaceae there are only faint and doubtful indications.
The general name of polypetalous is given to corollas having separate petals, while monopetalous, gamopetalous or sympetalous is applied to those in which the petals are united.
Regular gamopetalous corollas are sometimes campanulate or bell-shaped, as in (Campanula) (fig.
Finally the genera Pinguicula, Utricularia, Genlisea and Polypompholix belong to the gamopetalous order Lentibulariaceae.
Well-defined polypetalous and gamopetalous genera sometimes occur in the same order, and even Monocotyledons and Dicotyledons are classed together where they have some .striking physiological character in common.
Amongst Dicotyledons the gamopetalous forms are admitted to be the highest development and a dominant one of our epoch.
Of irregular gamopetalous corollas there may be mentioned the labiate or lipped (fig.