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.