There was but one author, during this period, who made any material contribution to the science of classification, and that was Joachim Jung of Hamburg (1587-1657). Jung is best known by his _Isagoge Phytoscopica_ (1678, ed. Vaget), the most philosophic and scientific treatise on plants that had appeared since the time of Aristotle, which is the foundation upon which the whole superstructure of plant-morphology and descriptive botany has since been erected. But it was in his _De Plantis Doxoscopiae Physicae Minores_ (1662, ed. Fogel) that he expressed his views on systematic Botany. He did not propound a system of his own, but he sought to arrive at the principles upon which a classification should be based, with the logical result that he rejected the time-honoured Theophrastian division of plants into Trees and Herbs. Though Jung failed to produce any immediate impression upon the Botany of his time, he powerfully influenced the great developments which took place in the eighteenth century. It so happened that Ray, as he mentions in his _Index Plantarum Agri Cantabrigiensis_ (1660), had obtained through Samuel Hartlib a MS. of the whole or part of Jung's _Isagoge_, which seems to have impressed him so much that he included many of Jung's morphological definitions in the glossary appended to the _Index_; and he subsequently embodied the _Isagoge_ in the first volume of his _Historia Plantarum_ (1686). It was from Ray's _Historia_ that Linnaeus learned the morphological principles and terminology of Jung which were the basis of his own work in descriptive Botany, and rendered possible the elaboration of his system of classification. But, in spite of Jung, the venerable division of plants into Trees and Herbs continued to hold its own for a time. As will be seen, it was still adhered to by Morison and by Ray, even after it had been shown to be quite untenable by Rivinus (_Introductio Generalis in Rem Herbariam_) in 1690, and did not finally disappear until the time of Linnaeus.