Functions of Seeds

The seed is important in carrying plant life through periods of unfavorable conditions as well as in distributing plants from place to place. Certain seeds are adapted to distribution by wind some of these have tufts of hairs (for example, poplar and milkweed), and some are winged (for example, maple and catalpa). Certain other seeds are adapted to distribution by water (for example, coconut), while still other seeds are carried by animals, in either the fur or the digestive tract. Seeds distributed by water require coats that are impervious to water in order to avoid premature germination. Such seeds eventually germinate when the seed coats are eroded away, as by wave action at the beach or by bacterial action. In some cases, such seeds germinate only after being in a fire.

The fruits of certain plants exhibit unique adaptations that aid in distribution. For example, some seeds are forcefully discharged from the fruit as a result of a buildup of internal pressure (touch-me-not, for instance). The seeds may be thrown a distance of several feet (as is the case with Impatiens). In such cases, a mere touch will cause a sudden outburst. The seeds of pansies and violets are shot from their pods one at a time. Mistletoe produces seeds that are sticky and adhere to the beaks of birds. The birds later scrape off the seeds on the bark of a tree elsewhere.