BOISSIER DE SAUVAGES, François. Methodus foliorum, seu plantae florae Monspeliensis, juxta foliorum ordinem, ad juvandam specierum cognitionem, digestae. Methode pour connoître les plantes par les feüilles. 1751.

First edition.
Boissier de Sauvages (1706-1767) offers with this book both a key to the identification of plants by the leaves and a proposal for botanical classification using the shape of the leaves.
A letter to Linnaeus serving as a preface sets out the principle, more convenient than the Linnaean method based on flowers and fruiting.
The two botanists will maintain a long correspondence and a pupil of Linné will even come to do his thesis in Montpellier on the local flora.