;http://www.geocities.com/CollegePark/Lab/2276/codesf.htm#1

to fern :size
  if :size<5[stop]
  fd :size/25         ; trunk
  lt 80 fern :size*.3 ; left branch
  rt 82 fd   :size/25
  rt 80 fern :size*.3 ; rite branch
  lt 78 fern :size*.9 ; spine
  lt  2 bk   :size/25
  lt  2 bk   :size/25
end

fern 400