What led young Lamarck to take up botanical studies, his botanical rambles about Paris, and his longer journeys in different parts of France and in other countries, his six years of unremitting labor on his _Flore Française_, and the immediate fame it brought him, culminating in his election as a member of the French Academy, have been already recounted. Lamarck was thirty-four when his _Flore Française_ appeared. It was not preceded, as in the case of most botanical works, by any preliminary papers containing descriptions of new or unknown species, and the three stout octavo volumes appeared together at the same date. The first volume opens with a report on the work made by MM. Duhamel and Guettard. Then follows the _Discours Préliminaire_, comprising over a hundred pages, while the main body of the work opens with the _Principes Élémentaires de Botanique_, occupying 223 pages. The work was a general elementary botany and written in French. Before this time botanists had departed from the artificial system of Linné, though it was convenient for amateurs in naming their plants. Jussieu had proposed his system of natural families, founded on a scientific basis, but naturally more difficult for the use of beginners. To obviate the matter Lamarck conceived and proposed the dichotomic method for the easy determination of species. No new species were described, and the work, written in the vernacular, was simply a guide to the indigenous plants of France, beginning with the cryptogams and ending with the flowering plants. A second edition appeared in 1780, and a third, edited and remodelled by A. P. De Candolle, and forming six volumes, appeared in 1805-1815. This was until within a comparatively few years the standard French botany. Soon after the publication of his _Flore Française_ he projected two other works which gave him a still higher position among botanists. His _Dictionnaire de Botanique_ was published in 1783-1817, forming eight volumes and five supplementary ones. The first two and part of the third volume were written by Lamarck, the remainder by other botanists, who completed it after Lamarck had abandoned botanical studies and taken up his zoölogical work. His second great undertaking was _L'Illustration des Genres_ (1791-1800), with a supplement by Poiret (1823). Cuvier speaks thus of these works: