What is called a perfect flower we will examine in the common buttercup of the fields. At the top of the stem we find a cup or calyx of five narrow, separate green leaves, called sepals; these form the outer wrapping of the bud, and maintain and protect the more delicate inner parts of a flower. Within the calyx is the corolla--five glossy, yellow, roundish petals, set in a circle; within this we have another ring of downy, bright-yellow stamens, and still within these, protected by all the others, certain yellow pistils, fewer and firmer in texture than the stamens. All of these four rings of parts are placed upon the fleshy, enlarged top of the stem, which is called the receptacle. The yellow of this flower is very yellow, and the stem and leaves are very green. The stem and leaves of our buttercups are hairy; the whole plant is provided with a sharp, stinging juice. The buttercup, as we have seen, is made up of four circles, each composed of several distinct parts. A flower with several petals is called polypetalous. Other flowers have but one petal; they are styled monopetalous. In fact, in such one-petaled flowers a number of petals have simply grown together. Let us take the morning-glory as an example. Pull off the calyx; it comes off as a whole, but is cleft half way down into five lobes, showing that it is truly composed of five united petals. Now pull the corolla from another calyx cup; it comes as a whole, and is not cleft as the calyx is, but it has five stripes, and at each stripe the margin has a little point, and we can make out very plainly that here are five prettily-pointed petals united into one, with a long tube made of the claws, and a beautiful wide margin made of the banners. Four-o’clocks, stramonium, Canterbury bells, phlox, and many other flowers have these one-petaled corollas. Such corollas differ greatly in shape, owing to the length and diameter of the tube and margin. In the polypetalous corollas we have the rich splendors of roses, from single to the fullest double, where cultivation has changed all stamens and pistils into petals. The polypetalous tribe give us also the lovely, perfume-filled chalices of the lilies; the peas, with their many-colored banners; the charming violets, with their spurred petals; the columbine, with its horns of plenty. Color of some kind is one of the distinguishing features of blossoms. Fragrance is another marked characteristic of plants, and is chiefly in the flower. There are plenty of scentless plants, yet the majority are full of perfume. Some few have a very disagreeable smell. Fragrance in plants comes from certain oils or resin laid up in different parts of the plant, whether in the leaves, bark, wood, fruit, seeds, or blossoms.