This is the third and final volume of Mueller's selected correspondence. It covers the last two decades of his life - his most productive period from a scientific point of view - including his work as Government Botanist of Victoria; his multifarious contributions to taxonomy, biogeography and economic botany; his engagement with the exploration of inland Australia, New Guinea and Antarctica; his manifold links with international science; and his evolving personal circumstances as one of the leading citizens of his adopted country. This volume contains a substantial historical introduction, and a further extension of the editorial apparatus developed in previous volumes.