Linnaeus is also criticised in the Vegetable System, more particularly for his unnecessary introduction of new names for plants; but here again Hill is full of praises for Linnaeus's descriptions of species.
Although opposed to the Linnaean system Hill recognised its value as a means of evolving order out of chaos, and to him falls the credit of introducing it into England.
Its first introduction was in his History of Plants (1751), but it was unsatisfactory since the Species Plantarum was not published until 1753. Hill next explained it in 1758[82], but it was not until two years later that the first British Flora, arranged on this system, appeared[83]. According to Pulteney[84], Hill performed this task "in a manner so unworthy of his abilities, that his work can have no claim to the merit of having answered the occasion: and thus the credit of the atchievement fell to the lot of Mr William Hudson F.R.S."
Mention has been made of Hill's Vegetable System[85]: a work which consists of 26 folio volumes and was undertaken at the suggestion of Lord Bute. It was commenced in 1759, and the date of the last volume is 1775, the year of Hill's death. No expense was spared in its production, the paper is of the best, and there are 1600 plates: with regard to these the title-page of the work states that they were designed and engraved by the author, but it appears from other sources that they cost four guineas each to engrave, and since it is stated on the auctioneer's announcement of the sale of the copyright (1782), together with some of the original drawings and the remaining sets, that the engravings were made by the best masters under the immediate supervision of the author, it must be concluded that Hill was not the actual engraver although he may have made the original drawings. Attention is drawn to this point, since it casts some doubts as to whether Hill engraved those plates, signed by him, illustrating some of his other works, for instance, The British Herbal, and A Method of Producing Double Flowers from Single[86], of which some are very good indeed, and, if Hill were the engraver, shew that he had considerable artistic and technical ability.
Naturally the plates in the Vegetable System are of uneven quality, some are very good and not only are pleasing from the artistic point of view, but also give a concrete idea of the plants represented. It is impossible here to criticize this work in detail; but some idea of its scope may be given. The first volume and part of the second is concerned with the history of Botany; the origin of Systematic Botany; the Systems of Caesalpinus, Morison, Ray, Tournefort, Boerhaave, Linnaeus, and others; morphology, anatomy, physiology; and the effect of heat, light, air, soil and water on vegetation. The rest of the work is occupied by descriptions of plants, both British and foreign, when the latter, the native country is mentioned; in all cases the medicinal properties are given.
It is hardly necessary to remark that notwithstanding the price of the work, 38 guineas plain and 160 guineas coloured, Hill lost considerably over its publication. From Mrs Hill's account[87], it appears that Bute undertook that Hill's circumstances should not be injured by the venture, an undertaking which was not kept; and further, after the death of Hill, Bute refused to compensate Mrs Hill for the unfinished last volume or to take the materials which had accumulated for it out of her hands. Allowing some discount for the natural exaggeration of a bereaved lady suffering from a grievance, there appears but little doubt that the Earl of Bute proved lacking in good faith.
Considered as a systematist there can be no doubt that Hill knew his plants; and although the systematists of the period were overshadowed by Linnaeus, Hill preserved his independence of thought, and did not hesitate to express his opinions when they differed from those of his great contemporary. Although he highly appreciated the work of Linnaeus he disliked his system of classification on account of its artificiality, and he intended to bring forward a natural system of his own. It is not, I think, too much to say that time has justified his criticism; and many of his minor differences have been warranted. For instance, Linnaeus merged the genera Valerianella and Linaria into those of Valeriana and Antirrhinum respectively; Hill however recognized the generic rank of the two former[88].
Incidentally, it may be remarked that the acceptance of the year 1753 as the starting-point for the citation of names by the Vienna Botanical Congress has been the cause of more general recognition of Hill's activity in this direction; thus in recent editions of British Flora his name is appended to many genera and species[89].
The Vegetable System gained Hill the Order of Vasa, from the King of Sweden, in 1774, so that he styled himself Sir John; he was also a Member of the Imperial Academy, and a Fellow of the Royal Academy of Sciences, Bordeaux.