In the sparsely inhabited, tropical portion of eastern Colombia is an ant tree known as the barrasanta. It is a small, slender tree with showy, red flowers which grows 25 to 30 feet in height. Both trunk and branches are hollow and filled with masses of vicious, biting ants. As soon as the tree is disturbed the insects swarm upon the invader. As a result the tree is generally left alone both by Indians and white settlers. The ants are protected by the branches and in turn protect the host with their fighting prowess. A curious shrub which grows out of enormous anthills found through the llanos region of western Colombia furnishes quite a different example of insect-plant association. The ants are “leaf cutters.” All other plant life avoids their immediate neighborhood. This particular shrub exudes a viscous, milky juice which traps any ants which try to climb toward its leaves. Hence the insects have learned to leave it alone and it enjoys the rich ant hill soil without competition from any other plants. _The Strange Behavior of Plants_ The behavior characteristics of some American plants are strange indeed. The compass plant, a bristly perennial of the aster family which grows in abundance over the prairies, is a living compass. It turns the edges of its leaves in a general north-south direction. Another American plant, the wild lettuce, does the same thing. The result is that when the intensity of sunlight is weakest in the morning and evening the flat surfaces of the leaves are in a position to receive the maximum available amount of light. At noon, when there is more light than the plant needs, only the edges of the leaves are turned towards the sun. Then there is the English ivy which arranges its leaves in a mosaic pattern so that about the greatest possible area is exposed to the light. Other plants show equally precise adaptations to their light requirements. It is all associated with the process of photosynthesis—i.e., the manufacture by the plant of carbohydrates out of carbon dioxide and water in the presence of light. The strength of light needed for this process varies somewhat with the particular plant and its conditions. The phenomenon is one of the most vital in creation, the transformation of the sun’s energy into the fuel of animal life. Without it life would be impossible.