Page:Popular Science Monthly Volume 15.djvu/26

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planation thus afforded of the nature and origin of these disused parts is endorsed by the fuller knowledge of their history; while, from a study apparently of insignificant interest, may be shown how certain of our living neighbors, along with ourselves, have, from lower states, and from the dawning epochs of the world, literally taken their place "in the foremost files of time."

As most persons who have attentively looked at any common plant can tell, four parts are included in a perfect flower. These parts or sets

PSM V15 D026 The wallflower.jpg
Fig. 1.

of organs, as seen in the wallflower, consist (Fig. 1), firstly, of an outer covering colored green, and named the "calyx" (ca). Then comes the blossom or flower itself, forming the "corolla" (co). Inside the corolla we find certain stalked organs, each bearing a little head or "anther," filled with a yellow dust, the "pollen." These organs are the "stamens" (st). Lastly, in the center of the flower, we note the "pistil" (p), or organ devoted to the production of "ovules." The latter, when duly fertilized by being brought into contact with the "pollen" of the stamens, become "seeds," and are capable of growing up, when planted, into new plants. Now, the botanist will inform us that it is a matter of common experience to find some individual plants of a species with well-developed petals or blossoms, and other individuals of the same species with petals in a rudimentary condition, thus proving that the production of imperfect parts in flowers occurs as an ordinary event under our own eyes, and under the common conditions of plant-life. The natural order of plants to which snapdragon belongs presents a peculiarity, inasmuch as in most of its members one of the five stamens is abortive or rudimentary. It should be borne in mind that the botanist possesses a highly interesting and exact method of ascertaining how many parts or organs should be represented in plants. He places his reliance in this respect on the working of what may be called the "law of symmetry." The operation of this law, which may be said to be founded on wide experience, tends to produce a correspondence in numbers between the parts in the four sets of organs of which we have just noted a flower to be composed. Thus, when we count five parts in the green calyx of a plant, we expect to find five blossoms or petals in its corolla; five stamens (or some multiple of five) and five parts (or