The reproductive structure of an angiosperm is the flower. Flowers differ in their shapes, colors, and sizes. They range in form from the simple buttercup to the complex orchid. Although there is a great diversity in their form, most flowers have the same basic parts.

The receptacle, which is located at the base of the flower, is the structure to which all flower parts are attached. The receptacle also connects the flower to the rest of the plant. The small leaflike structures above the receptacle are the sepals. All the sepals together form the calyx. Inside the sepals is a ring of brightly colored structures, the petals. All the petals together form the corolla. The corolla is usually the most noticeable part of the flower. Inside the corolla are the male reproductive structures, the stamens. Notice taht each stamen contains an anther, and a filament. The anther is the structure in which the male gametophytes, or pollen grains, are produced. The filament is a long thin stalk that attaches the anther to the receptacle. In the center of the flowr is the pistil, the female reproductive structure. The pistil contains three major parts: (1) the ovary, the structure that contains on or more ovules and developing gametophytes; (2) the stigma, the upper part of the pistil upon which pollen grains land; and (3) the style, the connecting stalk between the sigma and the ovary.

The ovary is the distinguishing feature of the angiosperm. It is the part that encloses first the developing gametophyte and later the developing seed. Gymnosperms have ovules, which later develop into seeds. Only in the angiosperms are the ovules enclosed inside the ovary.

The appearance of the basic flower parts can vary so much from one plant to another that the parts are sometimes difficult to identify. In a tulip, the sepals are brightly colored, rather than green. In the flower called butter-and-eggs, the sepals join with the petals, forming a structure called a spur.

In some species of plants there are male and female flowers. Such flowers are called imperfect flowers. Male flowers are called staminate flowers, called pistillate flowers, contain only pistils. The flowers of a corn plant are imperfect flowers. The tassels on top of the plant are the staminate flowers, and the young ears of corn are the pistillate flowers. Other plants, such as the tulip, contian both stamens and pistils in one flower and are called perfect flowers.