Cesalpino developed the first scientific classification system for flowering plants.

"Unlike the "herbals" of that period, it contains no illustrations. The first section, including thirty pages of the work, is the part of most importance for botany in general. From the beginning of the 17th century up to the present day botanists have agreed in the opinion that Cesalpino in this work, in which he took Aristotle for his guide, laid the foundation of the morphology and physiology of plants and produced the first scientific classification of flowering plants. Three things, above all, give the book the stamp of individuality: the large number of original, acute observations, especially on flowers, fruits, and seeds, made, moreover, before the invention of the microscope, the selection of the organs of fructification for the foundation of his botanical system; finally, the ingenious and at the same time strictly philosophical handling of the rich material gathered by observation. Cesalpino issued a publication supplementary to this work, entitled Appendix ad libros de plantis et quaestiones peripateticas (1603).

"Cesalpino is also famous in the history of botany as one of the first botanists to make an herbarium; one of the oldest herbaria still in existence is that which he arranged about 1550–60 for Bishop Alfonso Tornabono. After many changes of fortune the herbarium is now in the Museo di Storia Naturale di Firenze at Florence. It consists of 260 folio pages arranged in three volumes bound in red leather, and contains 768 species of plants. A work of some value for chemistry, mineralogy, and geology was issued by him under the title De metallicis libri tres (Rome, 1596). Some of its matter recalls the discoveries made at the end of the eighteenth century, as those of Antoine Lavoisier and René Just Haüy, it also shows a correct understanding of fossils.

"The Franciscan monk Charles Plumier gave the name of Cæsalpinia to a plant genus and Linnaeus retained it in his system. At the present day this genus includes approximately 150 species and belongs family Fabaceae, subfamily Cæsalpinioideae, which contains a large number of useful plants. Linnaeus in his writings often quotes his great predecessor in the science of botany and praises Cesalpino in the following lines:

Quisquis hic exstiterit primos concedat honores
Casalpine Tibi primaque certa dabit.

Digital facsimile from the Biodiversity Heritage Library at this link.