  Spatial distributions of morphogens provide positional information in
  developing systems, but how the distributions are established and maintained
  remains an open problem. Transport by diffusion has been the
  traditional mechanism, but recent experimental work has shown that cells can
  also communicate by filopodia-like structures called cytonemes that make
direct
  cell-to-cell contacts. Here we investigate the roles each may play
  individually in a complex tissue and how they can jointly establish a
reliable
  spatial distribution of a morphogen.
