Sequences of rbcL for 23 species of Nothofagus and three of Fagus have been determined and analysed to form phylogenetic trees. The two genera are well separated. The species of Nothofagus separate into lineages which correspond exactly with the subgenera recently defined on morphological grounds. The rate of evolution of the four subgenera is shown to be statistically the same and, using a reference date from palaeobotany, is found to be one nucleotide change in 6 Ma. This rate is used to derive the ages of the common ancestors of species in subgenera and it is tentatively concluded that intercontinental dispersal was possible in the early stages of the evolution of the genus.

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The complete amino acid sequence of the small subunit of ribulosebisphosphate carboxylase from spinach has been determined. There are 120 amino acids. The N-terminus of the protein is frequently blocked. There is a tyrosine-proline substitution at position 91 and the average molecular weight of the two forms is 13 897. The interest of the sequence data for students of physiology and evolution is discussed.

The first 40 amino acid sequences of the small subunit of ribulose bisphosphate carboxylase are given for 24 angiosperm species, three from each of eight families chosen because cytochrome c and plastocyanin sequences are already available. Using computer methods, these data have been analysed to yield minimal phylogenetic Steiner trees. A well defined minimal tree becomes apparent when data from all three proteins are combined. The root of the minimal tree is indicated by the node where a gymnosperm joins. The minimal tree is briefly compared with published phylogenies: in agreement is the divergence of the dicotyledons and monocotyledons from the root and the grouping of the Asteraceae and Caprifoliaceae; in disagreement, and a feature of all three proteins, is the close grouping of the Fabaceae with the Brassicaceae.