While the plant’s and, consequently, our debt to the leaf is seen to be tremendous, it cannot be ignored that, if plants produced nothing but leaves, the end of all plant life would come with the death from old age or disease of the present generation of plants. Except for those kinds that reproduce themselves by division or extension of their rootstocks, which bear buds, there would be no provision for increase. As only a comparatively small number of plants can reproduce by this method, it is obvious that something more must be provided to secure new generations of plants. Flowers, and the fruits and seeds which inevitably follow them, do this. All plants, with some exceptions to be noted later, produce flowers at some time in their life. In the case of the century plant, only once, after which they die. But except for ferns, mushrooms, seaweed, yeast, bacteria, and some other forms of so-called flowerless plants, a flower or blossom is to be found at some stage in the life of all plants.
If we examine the leaves of a goldenrod, we find that they are large below and diminish in size toward the top. Just below and among the flower clusters they are so much reduced in size and often changed in color that they cease to be ordinary foliage leaves, and are known as bracts. The occurrence of bracts is nearly universal in flowering plants, and they form not only an apparently transitional stage between leaves and flowers, but an actual one.