To provide evidence insight into the phylogenetic position of Itea L., we observed floral ontogeny of Itea yunnanensis Franch. under the scanning electron microscope (SEM) for the first time. The floral phyllotaxis is whorled and floral organogenesis follows centripetal pattern. Sepal initiation is in a two_fifths helical order. Petal initiation appears simultaneous, and petals grow at an ordinary rate. The haplostemony of this species arises slightly later than petals but earlier than gynoecium in initiation. Two carpels are free at the early stage of floral ontogeny, but incurve, get closer and become appressed to each other later. Paraffin transverse sections series of gynoecium at anthesis show that two carpels are connate on the ventral side through their entire length. At last, two carpels within the ovary fuse completely, forming two locules separated by a septum, the ventral vascular bundles in two stylar lobes are connected through the parenchyma, and the stigma lobes become fused. These observations are different from those by Bensel and Palser (1975). The gynoecia they described might be not mature, but rather at early developmental stage. We compared floral developmental pattern and floral structure of Itea with its related taxa. In I. yunnanensis petals grow in the way that is different from that of some related taxa such as Saxifragaceae sensu stricto, Hydrangeaceae, Ribes, Brexia . The developing pattern of gynoecium in I. yunnanensis is similar to that of some members in the Saxifragaceae sensu stricto and Hydrangeaceae. The treatment to raise taxonomic rank of Itea from genus to family, Iteaceae, is supported by our results.
