Trees of the Northern United States / Their Study, Description and Determination

by A. C. Apgar

The stamens and the pistil are the essential organs of a flower, because they, and they only, are needed in the formation of seeds. The pollen from the stamen, acting on the pistil, causes the ovules which are in the pistil to grow into seeds.

The calyx and corolla are called enveloping organs, since they surround and protect the essential parts.

The pieces of which the calyx is composed are called sepals. The Apple-blossom has five sepals.

The pieces that compose the corolla are called petals.

Fig. 10.

Kinds of Flowers.—When the petals are entirely separate from each other, as in the Apple-blossom, the flower is said to be polypetalous; when they grow together more or less, as in the Catalpa ([Fig. 10]), monopetalous; and when the corolla is wanting, as in the flowers of the Oak, apetalous.

When all sides of a flower are alike, as in the Apple-blossom, the flower is regular; when one side of the corolla differs from the other in color, form, or size, as in the Common Locust, or Catalpa, the flower is irregular.

In trees the stamens and pistils are often found in separate flowers; in that case the blossoms containing stamens are called staminate, and those containing pistils pistillate; those that contain both are called perfect. Staminate and pistillate flowers are usually found on the same tree, as in the Oaks, Birches, Chestnut, etc.; in that case the plant is said to be monœcious, and all trees of this kind produce fruit. Sometimes, however, the staminate and pistillate flowers are on separate trees, as in the Willows, which are diœcious; and then only a portion of the trees—those with pistillate flowers—produce fruit.

Arrangement of Flowers.—Flowers, either solitary or clustered, grow in one of two ways; either at the end of the branches, being then called terminal, or in the axils of the leaves, then called axillary. The stem of a solitary flower or the main stem of a cluster is called a peduncle; the stems of the separate blossoms of a cluster are called pedicels. When either the flowers or the clusters are without stems, they are said to be sessile.