Biology:
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.