GENTIANACEAE

The family consists of trees, shrubs, and herbs showing a wide range of colors and floral patterns. Flowers are actinomorphic and bisexual with fused sepals and petals. The stamens are attached to the inside of the petals (epipetalous) and alternate with the corolla lobes. There is a glandular disk at the base of the gynoecium, and flowers have parietal placentation. The inflorescence is cymose, with simple or complex cymes. The fruits are dehiscent septicidal capsules splitting into two halves, rarely some species have a berry. Seeds are small with copiously oily endosperms and a straight embryo. The habit varies from small trees, pachycaul shrubs to (usually) herbs, with ascending, erect or twining stems. Plants are usually rhizomatous. Leaves opposite, less often alternate or in some species whorled, simple in shape, with entire edges and bases connately attached to the stem. Stipules are absent. Plants usually accumulate bitter iridoid substances; bicollateral bundles are present. Ecologically, partial myco-heterotrophy is common among species in this family with a few genera such as Voyria and Voyriella lacking chlorophyll and being fully myco-heterotrophic.

Gentianaceae are distributed worldwide, but most species occur in temperate zones. According to Merckx et al., the neotropics were an important area for the early diversification events in Gentianaceae, most of which occurring during the Eocene. However, Pirie et al suggested that ancient vicariance cannot be ruled out as an explanation for the early origins of Exaceae across Africa, Madagascar, and the Indian subcontinent unless a strong assumption is made about the maximum age of Gentianales.

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