Just inside the calyx is what most people call the “flower,” which is really composed of more highly colored sepals, but which we call _petals_ (Figure 39A). Where these are joined together the collection, which forms tubular flowers like the lily of the valley, is called a _corolla_. It is, of course, the petals or corollas of flowering plants that give our landscapes their greatest beauty, their most gorgeous coloring. While this from one point of view amply justifies a prodigal nature in strewing the earth with beautiful flowers, the true value of the color to the plant is in quite other directions, which will be explained a little later. Toward the base of the corolla, or sometimes on the petals or sepals, may be found a series of slender appendages, usually threadlike or a little thicker, crowned at the top by a distinctly large knob. The individual appendage is known as a _stamen_ (Figure 39 C), its threadlike portion a _filament_ (Figure 39 C), and the knoblike top an _anther_ (Figure 39 C^{1}). Directly in the middle of the flower there is still another organ, usually swollen at the base, slender in the shank, and either thickened or branched at the tip. This central part of nearly all flowers is called collectively a pistil (Figure 39 D), its swollen base an _ovary_ (Figure 39 D), the slender shank the _style_ (Figure 39 D^{1}), and the thickened or branched tip a _stigma_ (Figure 39 D^{2}). A perfect and complete flower, then, is composed as follows: Calyx Corolla Stamens consisting Pistil consisting or + or + of filaments + of ovary, style, sepals, petals, and anthers, and stigma. The stamen is the male organ of reproduction and the pistil the female. The actual process of fertilization, pregnancy, the forming of the fruit and later the seed, and the latter’s birth of a new plant, comprise one of the most fascinating of those provisions of nature which secure the perpetuation of the plant world. In the life history of even the commonest weed along the roadside there is this constant renewal of life by sexual reproduction, just as in animals and in man. In the chapter on “How Plants Produce Their Young” will be found some account of this supreme function of flowers, after which, as if their usefulness were over, they wither and perish.