stamen, one of the four basic parts of a flower. The stamen (microsporophyll), is often called the flower's male reproductive organ. It is typically located between the central pistil and the surrounding petals. A stamen consists of a slender stalk (the filament) tipped by a usually bilobed sac (the anther) in which microspores develop as pollen grains. The number of stamens is a factor in classifying plant families, e.g., there are 5 (or multiples of 5) in the rose family and 10 in the pulse family. In most flowers the stamens are constructed so as to promote cross-pollination and to avoid self-pollination; e.g., they may be longer than the pistil or may be so placed in relation to the pistil (as in the mountain laurel and the lady's-slipper) as to prevent the pollinating insect from transferring the pollen of a flower to its own pistil. There may be differing maturation times for the stigma of the pistil and for the anther. In some plants there are some flowers (staminate) that bear stamens and no pistil and others (pistillate) that have a pistil and no stamens; these flowers may be borne on the same or on separate plants of the same species. In some highly developed flowers, especially double ones, and in some horticultural varieties (e.g., the geranium) the stamen may be modified into a sterile petallike organ.