The herbalists’ knowledge of plants must have been in the first place transmitted from generation to generation entirely by word of mouth, but as time went on, written records began to replace the oral tradition. The earliest extant European work dealing with medicinal plants is the famous Materia Medica of Dioscorides, which was accepted as an almost infallible authority as late as the Renaissance period. Dioscorides Anazarbeus was a medical man who probably flourished in the first century of the Christian era, in the time of Nero and Vespasian. Tradition has, however, sometimes assigned to him the post of physician to Antony and Cleopatra. His native land was Asia Minor, but he appears to have travelled widely. In his Materia Medica he described about five hundred plants, with some attempt at an orderly scheme, though, naturally, the result is seldom successful when judged by our modern standards of classification. The actual descriptions of the plants are very slight, and it is only those with particularly salient characteristics which can be recognised with any ease. Careful research on the part of later writers has however led to the identification of a number of the plants to which he refers. There is a famous manuscript of Dioscorides at Vienna, which is said to have been copied at the expense of Juliana Anicia, the daughter of the Emperor Flavius Anicius, about the end of the fifth, or the beginning of the sixth century. The character of the script settles the age within narrow limits. Juliana lived into the reign of Justinian, and was renowned for her ardent Christian faith, and for the churches which she built. The manuscript which bears her name is illustrated by a number of drawings, which are in some cases remarkably beautiful, and very naturalistic. A facsimile reproduction of this manuscript was published in 1906, and it is thus rendered accessible to students. Examples of the figures are shown on a reduced scale in Plates I, II and XV. [Illustration: _Plate II_ ‘Stratiotes’ [Dioscorides, Codex Aniciæ Julianæ, circa A.D. 500]. _Reduced._] The botanists of the Renaissance devoted a great deal of time and energy to the consideration of the writings of Dioscorides. The chief of the many commentators who dealt with the subject were Matthiolus, Ruellius and Amatus Lusitanus, and a discussion of the botany of Dioscorides formed an integral part of almost every sixteenth-century herbal.