While this literature was developing in the Mohammedan world, the tradition of Pliny and Solinus was transmitted to the Christian world of the seventh and succeeding centuries by Isidorus of Seville. This brings us to the remarkable poetical treatise on the virtues of precious stones by Marbodus, Bishop of Rennes, a work written at the end of the eleventh century, and often quoted as that of Evax; indeed, it purports to be by him and really contains a good part of the material composing the treatise of Damigeron or Evax. At the same time Marbodus drew freely upon Pliny, either directly or through Isidorus. For the Middle Ages this poem of Marbodus, already translated into Old French in the twelfth century, became known as the “Lapidario” _par excellence_, and furnished a great part of their material to medieval authors on this subject. Soon, however, extracts from the Arabic sources became available, and the whole mass of heterogeneous material was worked over and recombined in a variety of ways. [Illustration: Title page of the first edition of the poetical treatise on precious stones by Marbodus, Bishop of Rennes, printed in Friburg, 1531.] This complex origin of the traditions explains their almost incomprehensible contradictions regarding the virtues assigned to the different stones, and also the fact that the qualities of one stone are frequently attributed to another one, so that, in the later works on this subject, it becomes quite impossible to present a satisfactory view of the distinguishing qualities and virtues of the separate stones. The habit of copying, without discrimination or criticism, whatever came to hand, and the aim to utilize as much of the borrowed material as possible, is scarcely less a characteristic of the seventeenth and eighteenth century writers than it is of those of a later date. This is in part an excusable and even an unavoidable defect, but it should be minimized as much as possible. [Illustration: Title page of the first edition of the Greek treatise by St. Epiphanius on the Gems of the Breastplate, with a Latin version. Edited and issued at Zürich in 1566 (1565) by Conrad Gesner.]