One of Hill's more interesting works in this branch of Botany is his British Herbal[80]. In it are described a large number of plants which are illustrated by 75 copper plates engraved by various artists. None of these plates are of outstanding excellence, indeed many of them are very poor, and their quality is uneven. Those in the folio consulted by the present writer were ruined by being coloured.
The plants described are arranged on a system which is not altogether without interest as it, in a small degree, foreshadows later systems. It may be indicated by giving the characters of the first four classes.
Class 1. Plants whose flower consists of several petals, with numerous threads in the center, and is followed by a cluster of naked seeds.
Class 2. Plants whose flower consists of several petals, with numerous threads in the center, and whose seeds are contained in several pods.
Class 3. Plants whose flower consists of a single petal, and is succeeded by several capsules.
Class 4. Plants with the flower formed of a single petal, plain, and of a regular form and succeeded by a single capsule.
It will be seen that Hill relied much on the characters of the corolla and the gynaeceum. But the chief interest in this work is, perhaps, Hill's criticisms of Linnaeus. One example will suffice; Linnaeus is criticised for placing Myosurus among the pentandria polygynia and thus separating it from Ranunculus, Adonis, etc. Hill remarked that thus to separate these plants merely because the number of stamens in Myosurus is less than in Ranunculus is unreasonable since they agree in all other essentials. He himself, however, made a similar error, for it will be observed that in the system followed in the Herbal, Ranunculus falls into the first class and Helleborus into the second.
These criticisms of Linnaeus, however, are not all of an adverse nature; in many places Hill does not stint his praise; and he does not fail, after describing each Genus, to mention its position in the Linnaean System.
Pulteney[81] found it difficult "to reconcile the praises this author bestows on Linnaeus, in many of his writings, with the censures contained in his British Herbal." The difficulty is not very apparent; Hill sufficiently indicated his position in the following passage taken from the Sleep of Plants. "If our opinions have differed, 'tis upon a single Point; your arrangement of plants. In regard to that much greater article, the establishing their distinctions, and ascertaining their characters, I have always admired and reverenced you: to dispute your determinations there, were to deny the characters of nature.
"Free in the tribute of applause on this head, I have on the other been as open in my censures; equally uninfluenced by envy, and by fear. It is thus science may be advanced; and you will permit me to say, thus men of candour should treat one another."