In the plant world, the sex of an individual specimen is not always easily defined. Sexual reproduction takes place in flowers and these come in many forms and types. Plants have developed several variations which has added to their diversity and increased their prospects for survival.

The stamen is the male part of a flower. It consists of a filament (stalk) and the anther where the pollen is produced. The pistil consists of the stigma, style and ovary. It is the female part of the flower and produces the seeds after fertilization (pollination) takes place.

Many plants have "perfect" flowers which contain both male and female parts. Some of these plants may be fertilized by pollen produced by their own flowers. They are said to be self-fruitful and would include tomatoes, peaches, apricots and tart cherry. Other plants such as apples, pears, sweet cherries and Japanese plums will not accept the pollen from their own flowers. These plants must have a second variety nearby to act as a pollen source and are called non-self-fruitful plants.

Other plant species have separate male plants and female plants. Holly and ginkgo trees are examples. These plants are called dioecious and require the presence of both a male and female for pollination to occur. That is why you must have both a male and female holly plant to produce berries on the female.

Corn, cucumbers and walnut trees are monoecious plants. They have separate male and a female flowers but they are located on different parts of the same plant. The silk on corn is the female flower while the tassel which provides the pollen is the male.

Cucumbers are even more mixed up. Most cucumber vines produce both male and female flowers on the same vine (monoecious). Generally, the first flowers will be male followed as the vine grows with some female flowers and ending with males at the end of the vine. Female flowers have a swelling at the base which is the ovary that eventually becomes the pickle. Male flowers do not have this swollen base.

In the quest for top production, plant hybridizers have developed cucumber varieties that have either all male or all female flowers. Commercial growers plant mostly cultivars with only female flowers. When planting large fields, they mix in a few seeds from a totally male variety so that these vines will act as the pollen source.

Transfer of the pollen from the stamen to the pistil occurs in many different ways. For some plants, it is carried by the wind and may spread over long distances. Other plants require that insects such as bees crawl over the surface of the anther and carry the pollen to the pistil of another plant. Birds and even bats may also carry out the function for certain species of plants around the world.

Tomatoes generally pollinate themselves before the flower opens. Breezes toss the closed flower around causing the pollen to drop from the anther to the stigma. Greenhouse grown tomatoes often need to be artificially shaken to accomplish fertilization since there is no wind to do the job.

Cucumbers require pollination by honeybees. Commercial growers bring hives into the fields to assure good pollination. Greenhouse cucumbers, the so-called burpless types, are parthenocarpic which means that they develop fruit without having to be pollinated. That is why they are seedless.

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