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Wednesday, January 25, 2006

The Development of Flowers

A new group of plants, the angiosperms, appeared about 110 million years ago. These plants had developed a number of structural innovations, the most striking of which is the flower. Flowers enchant us with their beauty, delicacy, and variety of form, but they represent a very practical development. Plants, by growing flowers and fruit, formed partnerships with animals who provided transportation for pollen and seeds.

Some flowering plants still use wind to transfer their pollen to other plants. The grasses, growing thickly together in meadows and on plains, continue to rely on wind pollination.

Many flowering plants, however, use insects or birds to distribute their pollen. Insects can be lured to the flowers by a few drops of sweet nectar. Brightly colored petals guide the insects toward the nectar and pollen. Bees can fly for several miles in a day, and, if all members of a plant species come into bloom at about the same time, the bees spread their pollen far and wide. Pollen sticks to the hairy bodies and legs of insects, and is easily carried away. Many of the fruits that we eat are dependent on insect pollination.

Another invention of the Angiosperms is the development of the seed coat on their seeds. Each seed is enclosed in a tough little covering to help it to survive in the world until conditions favor successful germination and development..


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