Phyllotaxis is the study of the successive arrangement of radial parts of a growing plant, such as the leaves on a stem, or the seeds in the head of a sunflower. This application generates a simple phyllotaxic arrangement of circles, expanding outward at either a linear or an exponential rate. You can specify the angle between each circle (between 0 and 360 degrees), and you can determine rate of expansion using a pair of slider controls.