Canopy trees of the tropical rainforest flower and bear fruit at intervals that are irregular and often long.

In some species, flowering seems to occur after short, dry periods, yet there is no apparent reason why other species suddenly burst into flower.

Flowering, usually affects all the individuals of one species in an area, so that there is a good chance of cross-pollination.

Many canopy trees are pollinated by insects, but birds and bats also play a valuable role.

The seeds of most plants have some kind of mechanism to take them away from the parent.

Generally, the offspring do not grow close to the parent, because competition for light and water is intense. The neighborhood of the parent can be a dangerous place - seed-eating birds and insects tend to congregate there.

Conditions also change, so that the seed that produced the parent may have germinated in a clearing that no longer exists.

Seeds can be dispersed by water, wind or animals or water.

Water is only useful if it is moving, and it often allows seeds to be spread in only one direction.

Although the lower layers of the tropical rainforest are still, many large trees have wind-dispersed seeds. Ceiba pentandra, the silk-cotton, has seeds covered in silky fluff that can travel long distances. The seeds of some leguminous trees, such as Newtonia, have flattened seeds with a marginal wing.

Mahoganies, such as Khaya and Entandrophragma, have winged seeds. The Entandrophragma has a wing at only end, which causes the seed to spin as it falls.

The seeds of the Strophanthus, a type of liana, have a parachute of hairs on a long projecting stalk. Wind also disperses the minute seeds of orchids.

The tropical rainforest's most important seed dispersers are animals.

About 70 per cent of tree species in the forests of Ghana have fleshy fruits. Their seeds are hard and resistant to digestion, and pass unharmed through animals.

When the fruits are ripe, fruit-eaters such as monkeys, hornbills, toucans and fruit bats feast in the trees, and then scatter the seeds in their droppings. On the ground, tapirs, gorillas and elephants eat the fallen fruits.

Once a seed has been dispersed, it must germinate and establish itself successfully in the forest undergrowth.

Here, there is intense competition above ground for the small amount of light that reaches the forest floor, and below ground, for water and mineral nutrients.

Plants employ two strategies to survive in this hostile environment.

One group produces large seeds in comparatively small numbers. The food reserves in each seed allow it to establish and sustain a large seedling. This remains in the understory, growing very slowly perhaps for many years. If a tree falls, and makes a gap with more light and less root competition, the seedling takes advantage of the change.

Another strategy, adopted by many quick-growing species, is to produce innumerable tiny seeds. These do not germinate in undisturbed forest, probably because the composition of the light in the understorey inhibits them. The seeds begin to germinate as soon as a clearing is formed.