see also: DigitalSculpture
http://www.muonics.net/site_docs/work.php?id=41
and
http://www.flong.com/projects/dendron/
the work of Przemyslaw Prusinkiewicz:http://algorithmicbotany.org/papers/
And his helpful website:
“Visual Models of Morphogenesis: A Guided Tour”:
http://www.biologie.uni-hamburg.de/b-online/virtuallaboratory/