Phyllotaxis

Phylotaxy or phylotaxis is the mode of arrangement of leaves on the stem of a plant (from Ancient Greek "leaf" and "arrangement").
Phyllotaxy has a function: it avoids over-crowding of leaves, and exposes the leaves to the most sunlight for photosynthesis. The four main types of phyllotaxy are alternate, opposite, ternate and whorled.