What was the impact of Lavoisier's new elementary chemical analysis on the conception and practice of chemistry in the vegetable kingdom at the end of the eighteenth century? I examine how this elementary analysis relates both to more traditional plant analysis and to philosophical and mathematical concepts of analysis current in the Enlightenment. Thus I explore the relationship between algebra, Condillac's philosophy and Lavoisier's chemical system, as well as comparing Lavoisier's analytical approach to those of his predecessors, such as Baumé and Bucquet. With reference to the aims of vegetable analysis, I show how the dominance of elementary analysis devalued a tradition that sought to isolate immediate principles (plant extracts), marginalizing the chemical practices of many doctors and pharmacists in the context of the new chemistry in France.