A text dealing with plants and their properties, often medicinal. Medieval herbals were frequently illustrated. The study of plants formed part of natural philosophy during Antiquity. Among the major authors of botanical texts written from the fourth century B.C. to the fourth century A.D. are Aristotle, Theophrastus (Historia plantarum), Hippocrates, Crateuas, Pliny the Elder (Historia naturalis), Dioscorides (De materia medica), and Pseudo-Apuleius Platonicus (Herbarium). Several of these works were probably illustrated during Antiquity. Southern Italy (especially centers such as Squillace, Monte Cassino, and Salerno) preserved the classical interest in botany and its medicinal application into the Middle Ages. The Carolingian and Anglo-Saxon worlds did much to perpetuate interest in several botanical texts (notably the works of Dioscorides and Pseudo-Apuleius), England producing the first vernacular translation of the Herbarium, perhaps as early as 1000. These early medieval copies contain cycles of illustrations which seem to represent for the most part copies of Antique cycles. It is clear from the errors in these depictions that the illuminators had no direct knowledge of some of the plants, and they retained images of classical deities such as Diana, Asclepius (god of medicine), and Mercury as well as the centaur Chiron, legendary teacher of Asclepius. Illuminated herbals continued to be produced throughout the Middle Ages primarily as library books, and their illustrations became progressively more stylized. The Islamic world, however, had also preserved - and expanded - knowledge of classical botany, which from the late eleventh century on was transmitted to the West. At the medical school of Salerno in the mid-twelfth century, the Circa instans, containing remedies, or simples, from Latin and Arabic sources, was compiled. Some manuscripts of the Circa instans (also known as the Liber simplici medicina or Secreta salernitana) and the slightly later Tacuinum sanitatis, from northern Italy, have illustrations of plants based on the direct observation of nature rather than on images in earlier herbals. This more scientific trend was perpetuated in works such as the Herbolario volgare (Popular Herbal), an Italian translation by Jacopo Filippo of an Arabic treatise by Serapion the Younger, and initiated the Renaissance tradition of naturalistically illustrated herbals. See also Classical texts.