Tree

VII

Unusual Trees

There are many types of unusual trees around the world that exhibit a variety of interesting characteristics. Among these are prehistoric relics, trees that exhibit bizarre growth patterns or formations, and trees with interesting strategies for obtaining the air, water, and nutrients necessary for growth.

Like the ginkgo, the dawn redwood is old enough to be considered a living fossil. Its fossilized remains were studied and identified in the 1800s, and scientists believed that the tree had become extinct about 20 million years ago. In 1941, however, a Chinese botanist discovered living trees in an isolated valley in central China. Since then, the tree has been found in other places in China, and the fossil record indicates that millions of years ago it grew in Greenland and in North America as far south as California. Like other sequoias, the dawn redwood grows well from seeds, and seedlings have been planted throughout the Pacific Northwest and in Alaska. Specimen trees have also been successfully grown in many of the milder parts of the East Coast of the United States. Unlike other sequoias, the dawn redwood is deciduous and loses its leaves in the fall.

Although the banyan tree begins life with a single trunk, aerial roots grow down from its spreading limbs and take root. These roots enlarge, eventually becoming trunklike, and in old age a single tree may have the appearance of a small forest. The largest banyan, found on the island of Sri Lanka, has 350 major trunks and several thousand smaller ones. The name of the tree comes from a Hindu word for trader, because in many regions where banyans are found, traders and merchants use the tree’s shade while displaying their wares.

The baobab tree, the closely related bottle tree, and certain cactus trees have trunks with fleshy centers. These trunks store large amounts of water, enabling the trees to survive the arid conditions under which they grow. The trunk of the baobab may measure 9 m (30 ft) in diameter. The bottle tree has a bulging bottle-shaped trunk. Cacti, although frequently covered with spines, can yield water to a lost hiker even in the driest desert.

---

---

Although it is native to Africa, the sausage tree is cultivated as an ornamental in warm areas such as southern Florida and Hawaii. The sausage tree has large deep red flowers, which are replaced eventually by giant sausage-shaped fruits about 60 cm long. Both the flowers and fruits are borne on long stems hanging from the limbs of the tree.

The pencil tree, a native of Asia, is grown as an ornamental in Hawaii and elsewhere because of its odd twigs, which are swollen, pencil-like, and bright green. The twigs serve the tree in place of leaves, which are almost totally lacking. The pencil tree has strongly caustic sap. On contact with the skin the sap causes a rash, and it may even cause temporary or permanent blindness if it touches the eye.

Bald cypress trees, deciduous needle-leaf trees that grow in swampy areas, are unusual because of special breathing organs known as cypress knees. These organs are extensions from the root system that project above the usual water level and absorb oxygen from the air for use by the roots.

Strangler fig trees are an example of a parasitic method of development that occurs in several plant families. A seed is deposited by a bird, monkey, or other animal in a depression or a crotch of a limb. The seed sprouts and begins to develop, and roots eventually find their way to the ground, sometimes traveling 25 m (82 ft) or more. There the roots take hold and begin to enlarge toward each other, enclosing the trunk of the host tree. Finally, the roots join side by side to restrict the growth of the original tree, which eventually rots away, leaving the parasite standing as an independent plant.

	More from Encarta
	•  Presidential Myths Quiz •  Coffee break: Recharge your brain