Parts of the Plant
Before plants can produce seeds they have to be pollinated. Plants have a male stamen, consisting of the anther, which holds pollen suspended on a stalk called the filament. Plants will also have female parts called the pistil. The pistil contains the stigma, a sticky bulb held out by another stalk called the style. At the base of the style is the ovary.
In some plants the stamen and the pistil are in separate flowers, while in others they are both in the same flowers. Plants such as grasses that don't depend on pollinators may have no flowers at all.
Most plants have a nectary inside the flower. This produces a sweet liquid called nectar, which attracts insects, birds, bats or other pollinators. The flower may also have a bright color, which draws a particular pollinator. As the pollinator drinks the nectar, it also rubs against the anther, which causing the pollen to stick to its body.
The pollen then comes into contact with the stigma of another plant, where it sticks, fertilizing the plant. In wind pollinated plants such as grasses, no pollinating animal is involved at all. Instead, the plant releases large amounts of pollen into the wind, where it drifts into other plants. Once the pollen reaches the stigma, it forms a tunnel down into the ovary, where it fertilizes a seed.
The seed develops inside the plant, along with a mechanism to spread it. Fruiting plants use fruits to spread their seeds. An animal eats the fruit, swallowing the seed in the process. When that animal excretes the seed later, it is planted at a distance away from the parent. Other plants use the wind to distribute their seeds. Dandelions and cottonwood, for example, release large numbers of seeds with natural parachutes, which drift out and settle randomly where they reach the earth.
Some plants have burrs attached to their seeds. These seeds get stuck in the fur of animals, and fall down wherever they are rubbed off. In any case, once the seeds reach the ground, they wait dormant until they receive the right temperature, moisture and sunlight to start growing.