|| Fibonacci numbers appear in the arrangement
of leaves of the branches of some trees. The leaves grow in spirals around
each branch. The number of leaves in each full rotation (from one leave
out along a branch until the one directly above it is reached) is often
a Fibonacci number. Also, the number of rotations on each branch is often
a Fibonacci number. Some trees that display this pattern are beech trees,
poplars, willows, and elms.
A good outside link to follow for more on leaf rotations is, again, the "Practical Procedural Modeling of Plants" article, <www.td-grafik.de/artic/talk20030122/overview.html>.