L-system

An L-system (Lindenmayer system) is a parallel string-rewriting grammar used to model the recursive growth patterns of biological structures. Invented by Aristid Lindenmayer in 1968 to describe the development of algae, L-systems apply production rules simultaneously to all symbols in a string, generating fractal-like structures through iterated replacement. A simple L-system with two rules can produce the branching pattern of a tree, the venation of a leaf, or the spiral of a shell. The connection to recursion is direct: the same generative rule operates at every scale, producing self-similarity without explicit scaling. L-systems are the formal bridge between developmental biology and formal language theory.