Morison's chief occupation at Oxford was the preparation of his long promised _magnum opus_, the _Historia Plantarum Universalis Oxoniensis_. It was planned on a most extensive scale, and proved to be a laborious and costly undertaking. Morison impoverished himself in the preparation even of the one volume of it that appeared in his lifetime, though his many friends provided the cost of the 126 plates of figures with which it is illustrated, and the University advanced considerable sums of money. The work was to have been issued in three parts: the first part was to be devoted to Trees and Shrubs, and the other two parts to the Herbs. The volume published by Morison in 1680, and described as _Pars Secunda_, deals with only five out of the fifteen sections into which he classified herbaceous plants, although it extends to more than 600 folio pages. In the preface he gives as his reason for beginning with the Herbs rather than with the Trees and Shrubs, that he wished to accomplish first the most difficult part of his task lest, in the event of his death before the completion of the _Historia_, it should fall into the hands of incompetent persons. He did not live to finish his great undertaking. In November, 1683, he was in London on business connected with it: as he was crossing the Strand near Charing Cross, he was knocked down by a coach, and was so severely injured that he died on the following day. He was buried in the church of St Martin-in-the-Fields. His unfinished work did not, as he feared, fall into incompetent hands. It was entrusted by the University to Jacob Bobart the younger, who on the death of his father in 1679, had succeeded him as Keeper of the Physic Garden, and who also succeeded Morison as _Horti Praefectus_, but not as _Professor Botanices_; the Professorship remained in abeyance for nearly forty years. After much difficulty and delay, a second and final instalment of the _Historia_, the _Pars Tertia_, dealing with the remaining ten sections of herbaceous plants, was published in 1699, as a folio of 657 pages with 168 plates. The material at Bobart's disposal was fairly abundant, consisting of Morison's MS. of four more of his sections of Herbs, with notes upon the remaining six sections. But even so, the task of completion was a laborious one, for it involved the incorporation of references to the very many descriptions of new plants that had been published since Morison's death: it has been generally admitted that Bobart discharged it with commendable skill. [Illustration: _Plate II_ Great Gate of the Physic Garden Oxford: the elder Bobart in the foreground]