Agalinis Raf., consisting of about 40 species, is the largest, most wide spread and taxonomically complex genus of hemiparasites in the eastern U.S.A. and Canada. Part of the Scrophulariaceae until recently, Agalinis now appears to be more closely related to the Orobanchaceae based on current molecular data. Despite the recent flurry of studies, the evolutionary affinity of the genus within the family is unresolved. In addition, while shared floral, vegetative, morphological and anatomical features characterize each section within Agalinis, the phylogenetic relationships among the different sections remain unclear. Based on revisions by Canne-Hilliker, currently North American Agalinis is composed of seven sections. The work presented here examined the floral development of representative species from five sections of Agalinis in order to determine the developmental characters that result in the characteristic floral form of each section. Species from the sections Heterophyllae and Agalineae were studied previously. This study investigated A. linifolia, A. divaricata, A. pulchella, A. obtusifolia, and A. plukenetii from the sections Linifoliae, Tenuifoliae, Pedunculares, Erectae and Setaceae, respectively. The species differ in many of the developmental markers examined. Some of the differences occur in relative time of appearance, shape and size of floral primordia. The timing of style elongation relative to ovule formation and to anther development also differs. Variation also occurs in calyx characteristics, such as shape of lobes and relative size of lobes to throat. During mid ontogeny, shape of style, location of stigmatic papillae, form of filaments, and shape, size and orientation of anthers diversify among taxa. Close to anthesis species differ in bud shape, relative length of abaxial to adaxial corolla throats, shape and size of corolla lobes, as well as style and anther positions. Zygomorphy is established at inception of primordia and is accentuated or reduced to varying degrees during development.

Key words: Agalinis(Scrophulariaceae s.l.), development, flower, ontogeny, Orobanchaceae