  A new model for biological growth is introduced that couples the geometry of
an organism (or part of the organism) to the flow and deposition of material.
The model has three dynamical variables (a) a Riemann metric tensor for the
geometry, (b) a transport velocity of the material and (c) a material density.
While the model was developed primarily to determine the effects of geometry
(i.e. curvature and scale changes) in two-dimensional systems such as leaves
and petals, it can be applied to any dimension. Results for one dimensional
systems are presented and compared to measurements of growth made on blades of
grass and corn roots. It is found that the model is able to reproduce many
features associated with botanical growth.
