Henry Pearson (1870-1916) was an English botanist specialising in research on the Gnetophyta division of woody plants. In 1903 he was elected to the Henry Bolus Professorship of Botany at the South African College, Cape Town (now known as the University of Cape Town), and he was elected a Fellow of the Royal Society in 1916 shortly before his death. In 1915 Pearson was commissioned to write this volume for the Cambridge Botanical Handbooks series. Published posthumously in 1929, it was the first extensive study on the Gnetales order and the only such study in English published during the twentieth century. In it, Pearson investigates the morphology and reproduction of the three Gnetophyta genera and examines their relation to the angiosperms (flowering plants). His research on Gnetophyta was later used together with genetic studies to provide theories explaining the evolution of seed plants.