FLOWERS AND FRUIT 25 



The last of the four kinds of parts is found in the center 

 of the flower, and is called the pistil. It is this part which 

 forms the fruit and incloses the seed. 



The stamens and the pistil are the essential organs of a 

 flower, because they, and they only, are needed in the for- 

 mation 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. 



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 ~ Fig. 10. 

 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 monoecious, and all trees of 

 this kind produce fruit. Sometimes, however, the stam- 

 inate and pistillate flowers are on separate trees, as in 

 the Willows, which are dioecious; and then only a por- 

 tion of the trees those with pistillate flowers produce 

 fruit. 



