A Floral Ontogenetic Study in the Dipsacales

The floral ontogeny of five representative species (Lonicera periclymenum, Symphoricarpos albus, Centranthus ruber, Dipsacus sylvestris, and Knautia arvensis) of Dipsacales has been studied and compared with existing floral ontogenies in order to examine the unresolved systematic position of Dipsacales. The floral ontogeny of the species studied differs only in minor aspects. All inflorescences share a basic dichotomous branching pattern initiated in an acropetal direction. The flowers of Dipsacus and Knautia (Dipsacaceae) arise successively in contact parastichies and are grouped in heads. However, the earliest flowers in the heads of Dipsacus are initiated in pairs, making a connection with the other dipsacalean families possible. In Dipsacaceae an epicalyx with a mixed bract and bracteolar origin arises. The sepals arise as individual primordia in Lonicera and Symphoricarpos (Caprifoliaceae). In the other genera individual sepal primordia are not observed, but a sepaloid meristematic ring is formed ins...