Jacob Bobart the Younger was a son of Jacob Bobart the Elder (1599-1680), and succeeded his father as Hortus Praefectus of the Oxford Botanic Garden. Bobart the Younger was evidently a precocious botanist, as he received special mention for his contribution to the second edition of the Oxford Botanic Garden 'Catalogue' in 1658. Like his father, Bobart the Younger was an impressive plantsman, developed the fledgling garden and exchanged seed with a wide range of the botanical elite of the late-17th and early-18th centuries, particularly William Sherard (1659-1728), Hans Sloane (1660-1753), John Ray (1627-1705) and the Duchess of Beaufort (1630?-1714). Furthermore, he was involved with Robert Morison (1620-1683) and completed the third part of Morison's Plantarum Historiae Universalis Oxoniensis in 1699.
The importance of Bobart's Hortus Siccus is that it is a snapshot of a botanical collection made during an exciting period of Early Modern botanical investigation, provides a means of verifying the identities of names used in the two 'Catalogues' published for the Oxford Botanic Gardens in 1648 and 1658 and illustrates the range of plants that were being grown during the period. Furthermore, the specimens in the Hortus Siccus reveal interesting applications of common names and Druce credits the collection as containing some of the first Oxfordshire records of native British plants.
The first mention of Bobart the Younger's herbaria is to be found in Evans' prose poem Vertumnus (1713).
Additional references to the herbaria are to be found in a list of the books in Bobart's library, where two items are mentioned; a Hortus Siccus of 38 volumes and mixed Horti Sicci of eight volumes. All subsequent histories of the Botanic Garden in Oxford make reference to the herbarium of Bobart the Younger as comprising two collections; the collections associated with the publication of Robert Morison's Plantarum Historiae Universalis Oxoniensis, known as the Morisonian Herbarium, and the more poorly known 'Bobart's Hortus Siccus. The first explicit reference to the latter collection in Oxford was by Daubeny in 1853, when he described the contents of the Oxford Herbarium as Henry Fielding's bequest was added.
Bobart's Hortus Siccus comprises mounted specimens (usually one taxon per sheet) that are labelled only with Latin polynomials and common names. The sheets were originally bound together but are now stored as separate sheets in 16 Solander boxes (the period when the bound volumes were cut-up is unclear), and arranged according to Morison's Sciagraphia. The majority of labels are in Bobart the Younger's hand, although there are some later annotations, including those of George Claridge Druce. All the specimens are undated and unlocalised. Vines and Druce placed considerable weight on a manuscript note dated 24th November 1666 to indicate the date of the collection, and considered that the specimens were collected entirely by Bobart and that the majority were from the Botanic Gardens and Oxfordshire. There are indices at the start of some of the volumes, which Druce used to suggest that the sheets were originally bound as twelve volumes of herbs, and two volumes of Fructices. However, the indices were made on paper from the reign of George III, long after Bobart the Younger had died.