Using the ergodic theory of nonnegative matrices, conditions are
obtained for the $L^2$ and almost sure convergence of a supercritical multitype
branching process with varying environment, normed by its mean. We also give
conditions for the extinction probability of the limit to equal that of the
process.
¶ The theory developed allows for different types to grow at different
rates, and an example of this is given, taken from the construction of a
spatially inhomogeneous diffusion on the Sierpinski gasket.