Silk Cotton Family (Bombacaceae)

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Silk Cotton Family (Bombacaceae)

The silk cotton family (Bombacaceae) is a group of about 200 species of tropical trees, some of which are of commercial importance as sources of lumber, fibrous material, or food. Species in the silk cotton family occur in all regions of tropical forest, but they are most diverse in Central and South America.

Biology of silk cotton trees

Silk cotton trees often attain a very large size, and can be taller than 98 ft (30 m). Their trunks are commonly of a peculiar, bottom-heavy, bottle shape, and their wood is usually soft and light in density. Many species in this family have buttresses at the base of their stem. The leaves of silk cotton trees are arranged alternately along the stem, have a toothless margin, may be simple or compound, and are typically shed during the dry season.

The flowers of trees in the silk cotton family are large and attractive, and develop during the leafless season. The fruit is a capsule, and the seeds commonly have long, silken hairs attached.

Economic importance

Various species of trees in the silk cotton family are economically important. Some species are harvested for their wood, which is rather soft and can be easily carved into dugout canoes and other useful products. Balsa wood is an extremely light yet strong wood that is obtained from the fast-growing balsa tree (Ochroma pyramidale ). This species is native to tropical forests of Central and northern South America, but most balsa wood is now harvested from plantations. Balsa wood is widely used to make architectural and other models, and to manufacture airplanes, flotation devices, and bottle corks.

Balsa wood was also used to construct the Kon Tiki, a simply-built raft used by Thor Heyerdahl, an anthropologist and adventurer. Heyerdahl crossed the Pacific Ocean from east to west in 1947 to test his theory about the movements of pre-historic peoples. In part, Heyerdahl’s ideas were based on the observation that the sweet potato (Ipomoea batatas ) had been cultivated by pre-historic peoples in tropical America, Oceania, and southeast Asia. Heyerdahl hypothesized that there had been exchanges of goods and information among these far-flung peoples, and they may have used simple balsa rafts or other vessels as a means of trans-oceanic transportation.

Kapok is a very fluffy material made from the abundant silken hairs that are attached to the ripe seeds of several species in the silk cotton family. Most important in this respect is the silk cotton or kapok tree (Ceiba pentandra ), originally from the tropical Americas but now widely planted in Africa and Asia. Less prominent as a source of kapok is the silk tree (Bombax ceiba ) of southern Asia. The kapok is derived from long, fine hairs that develop from the inner wall of the 4-6 in (10-15 cm) long seedpods of these trees. The silken hairs are not attached to the seeds, as they are in cotton (Gossypium hirsutum), an unrelated fiber-producing plant. A mature kapok tree can be as tall as 98 ft (30 m), and can yield up to 11 lb (5 kg) of fluffy fibers each year. Kapok is commonly used for stuffing cushions, mattresses, and furniture, and for other purposes that require a soft, voluminous filling. Kapok is water repellant and extremely light, but it tangles easily, is somewhat brittle, and tends to disintegrate eventually. In recent decades, kapok has been increasingly replaced by synthetic foams for many of its previous uses as stuffing.

The baobab trees (Adansonia spp.) of Africa and India are of religious importance to some indigenous peoples, who consider this species to be a tree-of-life. One West African belief holds that the first human was born from the trunk of a baobab tree, whose grossly swollen stems somewhat resemble the profile of a pregnant woman. It was further believed that after birth, that first human was nurtured by the vaguely breast-shaped fruits of the baobab. This interesting species is pollinated by plants, which live in small cavities that are associated with spines on the twigs and branches of the baobab tree.

Durians are among the world’s most interesting edible fruits, and are gathered from the durian tree (Durio zibethinus ). Durian fruits can be as large as 8 in (20 cm) in size, and have a greenish, spiny exterior, and

KEY TERMS

Buttress —A structure that many trees of humid tropical forests grow at their base to stabilize the tree against the swaying forces of the wind. Buttresses can occur as broadened bases of the trunk, or as large, vertical projections from the base.

Kapok —A fluffy, white material derived from the fruits of several species in the silk cotton family, and commonly used as a stuffing for pillows, mattresses, and similar items.

a whitish, custard like interior. Durian fruits have a foul, sulphurous smell, but if their rather disgusting aroma can be ignored, these fruits are delicious to eat. Durians are especially popular in Southeast Asia. Because of the foul smell of durian fruits, many hotels in that region have signs posted that ask their guests to not eat this food in their rooms.

See also Natural fibers.