No one knows why the maple sap runs upwards in spring. This force is not explained, but it is powerful enough to move engines if it were harnessed. It is cellular force, not directly propelled from the earth through the roots, for if a maple is cut, the sap still runs upward through the trunk. There is no heart in the trees as in the human body, no pump visible and beating, but a pure force, elemental and almost spiritual in its source. It is life force expressed through matter.