[Illustration: FIG. 68. A horse-chestnut stem showing leaves, buds, and scars where last year's leaves dropped off.] [Illustration: FIG. 69.--AN UNDERGROUND STEM Buds show distinctly at points indicated by _b_.] To understand how this comes about it will be necessary to study the parts of the flower and find out their individual uses or functions. PARTS OF A FLOWER If we take for our study any of the following flowers: cherry, apple, buttercup, wild mustard, and start from the outside, we will find an outer and under part which in most flowers is green. This is called the calyx (Figs. 70-74). In the buttercup and mustard the calyx is divided into separate parts called sepals. In the cherry, peach and apple, the calyx is a cup or tube with the upper edge divided into lobes. Above the calyx is a broad spreading corolla which is white or brightly colored and is divided into several distinct parts called petals. The petals of one kind of flower are generally different in shape, size and color from those of other flowers. In some flowers the petals are united into a corolla of one piece which may be funnel-shaped, as in the morning glory or petunia of the garden, or tubular as in the honeysuckle, wheel-shaped as in the tomato and potato, or of various other forms. Within the corolla are found several bodies having long, slender stems with yellow knobs on their tips. These are called stamens. The slender stems are called stalks or filaments and the knobs anthers. The anthers of some of the stamens will very likely be found covered with a fine, yellow powder called pollen. This pollen is produced within the anther which, when ripe, bursts and discharges the pollen. The stamens vary greatly in number in different kinds of flowers. In the centre of the cherry, peach, or mustard flower will be found an upright slender body called the pistil. In the peach and cherry the pistil has three parts, a lower rounded, somewhat swollen part called the ovary, a slender stem arising from it called the style, and a slight enlargement at the top of the style called the stigma. The stigma is generally roughened or sticky. If the ovary is split open, within it will be found a little body called an ovule, which is to develop into a seed. In the apple flower the pistils will be found to have one ovary with five styles and stigmas and in the ovary will be several ovules. In the buttercup will be found a large number of small pistils, each consisting of an ovary and stigma. The parts of different flowers will be found to vary in color, in shape, in relative size and in number. In some flowers one or more of the parts will be found wanting. Examine a number of flowers and find the parts. FUNCTIONS OF THE PARTS OF THE FLOWERS Now what are the uses of these parts of the flower? [Illustration: FIG. 70.--FLOWER OF CHERRY. _a_, pistil; _b_, stamen; _c_, corolla; _d_, calyx; _e_, section of flower showing ovary with ovule. (Drawing by M.E. Feltham.)]