Abstract:

The floral organogenesis of Hypericum przewalskii（Hypericaceae） was observed under scanning electron microscope. Two bract primordia occur first， and the flower primordium develops in the package of the bract primordia. Followed the initiation of bract primordia， five sepals are initiated by 2/5 circumference spiral. With the sepal primordia initiated， the angles between the sepal interstices swell up into large protuberances which become differentiated as common stamen-petal primordia. Five common stamen-petal primordia initiated simultaneously. Petal primordia are separated from the lower half of the common stamen-petal primordia by a median slit. The remaining upper half of the common stamen-petal primordia grows into a hemispherical structure， thus the five stamen primordia initiate opposite to the petal primordia. Then the stamen primordia sequentially differentiated from the inside to the outside to produce the secondary stamen primordia. With the development of the secondary stamen primordia and increasement of primordia， fascicled stamens were formed. When the secondary stamen primordia initiated， the five carpal primordia initiated in a simultaneous type. The development way of the fascicled stamens in H.przewalskii indicated that fascicled stamens in Hypericum may originate from haplostemonous structure. The significant difference in patterns of petal and stamen primordia between Hypericaceae and Clusiaceae supports the viewpoint of APG Ⅲ classification that Hypericaceae are separated from Clusiaceae.

Key words: Hypericaceae, Hypericum przewalskii, floral organogenesis, systematic implication