Flower Structure: Flower stalk is called the pedicel, and at the very end where the other flower parts are attached is called the receptacle. 4 types of floral appendages, sepals, petals, stamens and carpels. Most flowers have all four, and are called complete flowers, typically having 3, 4, 5, or more appendages of each type. Sometimes flowers lack two or more basic appendages, and are called incomplete flowers.
Sepals: lowermost and outermost of the four floral appendages, and are modified leaves that surround and enclose the other flower parts as they mature. Typically they are the thickest, toughest, and waxiest of the flower parts. All the sepals together are called the calyx.
Petals: Above the sepals are the petals, which the petals all together make up the corolla. The sepals and petals together are called the perianth. Petals contain pigments other than chlorophyll, have few or no fibers, and tend to be thinner.
Stamens: Above the petals. Known collectively as the androecium. Frequently called the 'male' parts of the flower. Have two parts, the filament (stalk) and the anther (where pollen is actually produced). The anther is composed of diploid cells, and in the anther there are four long columns of tissue that become distinct as cells enlarge and prepare for meiosis. These microspore mother cells (microsporocytes) continue to enlarge, undergoing meiosis and each producing four microspores. Neighboring anther cells in another layer called the tapetum act as nurse cells. Microspores grow and expand to form an especially resistant wall, and are then called pollen. The anthers open along a weak line and then release the pollen.
Carpels: Carpels make up the gynoecium, which are located at the highest level on the receptacle. They have three main parts, the stigma (catches pollen grains), the style (elevates the stigma to a useful position) and the ovary (where megaspores are produced). Some flowers can have 0 to many carpels. They are usually fused together into a single compound structure (frequently called the pistil). Inside the ovary there are placentae, which are regions that bear small structures called ovules. These have a short stalk (funiculus) which carries water and nutrients to the ovule. The ovule has a central mass of parenchyma called an nucellus. The nucellus is almost completely covered except for a small hole (micropyle) at the top. Some nucellus cells located in the ovule enlarge in preparation for meiosis, (aka megaspore mother cells/megasporocytes) After this, three of the four megaspores degenerate, and only one survives. This ovule develops into a seed after fertilization.