The _Junger Mania_, a plant allied to the Mosses, shows knowledge of the laws of mechanics when it uses a natural spring coiled in a small tube to project its seeds out into the world. Seeds of fresh-water Algae swim about for a few hours after leaving their mother-plant, vibrating their cilia with great rapidity. It is the ability of certain one-celled plants to move about freely which causes considerable discussion as to whether they are really not animals. The Diatoms are examples. They propel themselves through the water by oscillating their whole bodies from side to side. To reverse their direction they go backward like a ferryboat. The ancients as far back as Aristotle recognized the sensitiveness of plants to light and their eager use of its life-giving properties. In fact, one has only to watch the Sun-Flower follow the orb of day across the heavens to realize that there must be something vital in sunlight for the plants. What interests us is that they have the instinct or the knowledge to so present their surfaces to the light that they receive a maximum benefit from its influences. From the aristocratic indoor potted plant to the wild trees and shrubs on the edge of a thicket, we notice a vigorous straining toward the light. Each leaf is tilted at just the right angle to receive the largest possible share of energy, for the leaves are starch factories for which the sun furnishes the motive power. Botanists tell us that this heliotropism or turning motion toward the light is due to the tendency of most leaves to arrange themselves perpendicularly to the sun’s rays. Tendrils may be apheliotropic or tend to turn away from the light. Morning Glories or Wistaria, which climb up whatever support is handy, exhibit insensibility to light no matter from what angle it strikes. Stems, flower and leaves of all plants each give a different and scientific reaction to light in a way which looks much like directing thought. Nothing is more scientific than the skill with which plants co-operate with gravity in constructing their root systems. The roots are often trained to grow out horizontally and resist gravity for a certain distance. Then they gracefully yield to its pulling power, and, curving their tips downward, grow straight toward the center of the earth. Any secondary roots which are sent out again start horizontally to repeat the above process on a smaller scale. All this makes for an efficient, well-balanced root-system.