As printing became available, it was promptly used to publish herbals, the first printed matter being known as incunabula. In Europe, the first printed herbal with woodcut (xylograph) illustrations, the "Puch der Natur" of Konrad of Megenberg, appeared in 1475. Metal-engraved plates were first used in about 1580. As woodcuts and metal engravings could be reproduced indefinitely they were traded among printers: there was therefore a large increase in the number of illustrations together with an improvement in quality and detail but a tendency for repetition.