Thunberg spirea (Spiraea thunbergii). Coloured scanning electron micrograph (SEM) of a flower of Thunberg spirea, a member of the rose family, found in China and Japan. The small (8 millimetre diameter) flowers have five petals. They appear on the branches in late winter to early spring before the new leaves appear. The flower contains the reproductive parts of the plant. The stamens, comprising filaments topped by pollen grain (male sex cell) producing anthers (pale green), surround the stigmas (orange). The stigma is the top of the carpel in which the ovules (female sex cells) are located. Magnification unknown.