Reference also may be made to Hill's views on reproduction[78]; he considered that the pollen grain contained the embryo which was set free by the bursting of the grain after it had been deposited upon the stigma. The stigmatic hairs or papillae were supposed to be the ends of tubes into which the embryos entered, made their way into the placenta, and thus arrived into the "shells of the seeds" (the ovules). It is unnecessary to point out the absurdities of these ideas, but it may be mentioned that Hill's interpretations of his observations were at fault rather than the observations themselves. Thus, judging from his figures, he saw the contents of the pollen grain, the appearance of which, under the conditions of observation, might easily suggest the idea of an embryo. Also he noticed that the pollen grains burst in a little while when placed in water, a phenomenon which was rediscovered 138 years later[79], and he therefore thought that a similar bursting, with a consequent setting free of the embryo, would take place on the wet stigma of the lily, for example. _Taxonomy._ 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.