Theophrastus's Enquiry into Plants or Historia Plantarum (Greek: Περὶ φυτῶν ἱστορία, Peri phyton historia) was, along with his mentor Aristotle's History of Animals, Pliny the Elder's Natural History and Dioscorides's De Materia Medica, one of the most important books of natural history written in ancient times, and like them it was influential in the Renaissance. Theophrastus looks at plant structure, reproduction and growth; the varieties of plant around the world; wood; wild and cultivated plants; and their uses. Book 9 in particular, on the medicinal uses of plants, is one of the first herbals, describing juices, gums and resins extracted from plants, and how to gather them.
Historia Plantarum was written some time between c. 350 BC and c. 287 BC in ten volumes, of which nine survive. In the book, Theophrastus described plants by their uses, and attempted a biological classification based on how plants reproduced, a first in the history of botany. He continually revised the manuscript, and it remained in an unfinished state on his death. The condensed style of the text, with its many lists of examples, indicate that Theophrastus used the manuscript as the working notes for lectures to his students, rather than intending it to be read as a book.
Historia Plantarum was first translated into Latin by Theodore Gaza; the translation was published in 1483. Johannes Bodaeus published a frequently cited folio edition in Amsterdam in 1644, complete with commentaries and woodcut illustrations. The first English translation was made by Sir Arthur Hort and published in 1916.
The Enquiry into Plants is in Hort's parallel text a book of some 400 pages of original Greek, consisting of about 100,000 words. It was originally organised into ten books, of which nine survive, though it is possible the surviving text represents all the material, rearranged into nine books rather than the original ten. Along with his other surviving botanical work, On the Causes of Plants, Enquiry into Plants was an important influence on science in the middle ages. On the strength of these books, the first scientific inquiries into plants and one of the first systems of plant classification, Linnaeus called Theophrastus "the father of botany".
Theophrastus's two plant books have similar titles to two books on animals by his mentor Aristotle; Roger French concludes that he was effectively "doing a peripatetic exercise" in identifying regularities in and differences between plants, in the manner of Aristotle with animals. However, he went beyond Aristotle in describing seeds as parts of the plant; Aristotle, French argues, would never have described semen or embryos as parts of an animal.
Theophrastus made use of a variety of sources for the book, including Diocles on drugs and medicinal plants. Theophrastus claims to have gathered information from drug-sellers (pharmacopolai) and root-cutters (rhizotomoi). Plants described include poppy (mēkōn), hemlock, (kōnion), wild lettuce (thridakinē), and mandrake (mandragoras).
The surviving texts are the notes that Theophrastus used in teaching, and they were continually revised. He referred to earlier books in the Lyceum library including Democritus, sometimes preserving fragments of books otherwise lost. He mentions about 500 species of plant.