Spring seems to give a new impulse to life, especially to vegetable life, which always responds promptly to the genial rays of the sun. During the winter, in our climate, the cells which form our trees are contracted by the cold and when the warm days cause them to resume their natural size, a small vacuum is formed in each cell, which the first warm days proceed to enlarge by thawing only the trunk and branches of the tree, leaving the roots below embedded in frozen soil from which but little moisture can be drawn, while evaporation draws moisture from the trunk and branches with irresistible force. A warm rain now comes, thaws out the soil, and sets the juices therein contained in motion. An immediate rush of sap up the trunk of the tree is the result. It clears out the pores or channels, as a spring freshet clears out the water courses, it rushes into the branches, and the branches rejoice and put on their livery of green; it rushes out through the porous surface of the limbs and rises in the air in the form of vapor, while that which does not escape becomes charged with life and returns down a devious pathway and lays the foundation for another season's growth. But why should the sap ascend the tree? This is only one of many questions that the tree will not answer and no one else ever has answered. If we take a strip of blotting-paper and insert one end of it in an ink-well, the ink immediately begins to climb up the blotting-paper by means of the force known as capillary attraction. Here, says the seeker for truth, is the reason for the ascent of sap, and many profound authors have agreed that he is right. Others claim, however, that he is wrong, while still others think he is only partly wrong and that this force has something to do with it. If we cut the roots from a tree and insert the stem in water we will soon find that this force is not the sole cause for the ascent of sap. Another student has made experiments with the force called diffusion, and claims that this explains the rise of sap to such remarkable heights; but diffusion does not work fast enough and hence must be thrown aside. Another finds that water is imbibed through fine porous substances with great force and that air can thus be compressed to several atmospheres, and this force is affirmed to be the one at work in our trees. But the fact that the amputation of the leaves and branches checks the ascent is brought forward and this theory falls to the ground. The fact that liquid films have a tendency to expand rapidly on wetable surfaces was next advanced, but the objection to the first theory met it at once.