The perception of natural affinities among plants which, in the sixteenth and seventeenth centuries, was gradually, in a dim, instinctive fashion, arising in men’s minds, is perhaps best expressed in the work of Gaspard Bauhin, especially in his ‘Pinax theatri botanici’ (1623). This work is divided into twelve books, each book being further sub-divided into sections, comprehending a variable number of genera. Neither the books nor the sections have, as a rule, any general heading, but there are certain exceptions. For instance, Book II is called ‘de Bulbosis,’ and a section of Book IV, including eighteen genera, is headed ‘Umbelliferæ.’ Some of the sections represent truly natural groups. Book III, Section VI, for example, consists of ten genera of Compositæ, while Book III, Section II includes six Crucifers. Other sections contain plants of more than one family, but yet show a distinct feeling for relationship. For instance, Book V, Section I includes _Solanum_, _Mandragora_, _Hyoscyamus_, _Nicotiana_, _Papaver_, _Hypecoum_ and _Argemone_—that is to say four genera from the Solanaceæ followed by three from the Papaveraceæ. The common character which brings them together here is, no doubt, their narcotic property, but, although no definite line was drawn between the plants belonging to these two widely sundered families, the order in which they are described shows that their distinctness was recognised. Some of Bauhin’s other groups, however, which, like that just discussed, are distinguished by their properties, or, in other words, by their chemical features, have no pretension to naturalness from a morphological standpoint. This is the case with the group described in Book XI, Section III under the name of “Aromata,” which consists of a heterogeneous assemblage of genera belonging to different orders, which are only connected by the fact that they all yield spices useful to man. [Illustration: Text-fig. 70. “Plantago major” = Plantain [Fuchs, De historia stirpium, 1542]. _Reduced._] [Illustration: Text-fig. 71. “Althæa Thuringica” = _Lavatera thuringica_ L. [Camerarius, Hortus medicus, 1588].] There is no doubt that, on the whole, Bauhin was markedly successful in recognising affinities within small cycles, but he broke down on the broader question of the relationships between the groups of genera so constituted. This is, however, hardly surprising when we remember how much difference of opinion exists among systematic botanists, even to-day, upon the subject of the relations of the orders to one another.