Auxins themselves are a class of plant hormones recognized for their ability to elongate and divide the cells of plant. Auxins are mainly produced at the various meristems of plants and are responsible for plant growth and other factors. One of these other factors are phototropism. It was observed by Charles Darwin that some plants bent in the direction of light. However, when the tip of the plant was covered this bending did not occur, and when the tip was the only part remaining uncovered the bending still did. Further research has shown that in many plants the auxin producing area is important in this phototropic characteristic. The apical meristem at the center of the plant stem shown above is an auxin producing area of the plant.