had long served to include a great number of distinct forms, though the separation of these groups had nowhere in truth been carried out with logical precision. These remarks are important as serving to show in the most decisive manner the incorrectness of the assertion, that the study of organisms sprang from the recognition of individual species; that it is this which is directly given, and that without it no advance in the science is possible. The historical fact rather is, that descriptive botany began often, perhaps most often, not with species but with genera and families, that very often at first whole groups of forms were conceived of as unities, which had to be divided later and of set purpose into separate forms; and up to the present day one part of the task of the systematist is to undertake the splitting up of forms previously regarded as identical. The notion that the species is the object originally presented to the observer, and that certain species were afterwards united into genera, is one that was invented in post-Linnaean times under the dominion of the dogma of the constancy of species; it happened so sometimes, but just as often the genus was the object first presented, and the task of the describer was to resolve it into a number of species. In the 16th century the conception neither of genus or species had yet been defined; for the botanists of that period genera and species had the same objective reality. But, in the process of continually making the descriptions of individual plants more exact, forms once separated were united, and those before assumed to be identical were separated, till it gradually became apparent that both operations must be pursued with system and method. It cannot therefore be exactly said that somebody first established the species, another the genus, and a third person again the larger groups. It is more correct to say that the botanists of the 16th century carried out this process of separation up to a certain point without intending it, and in the effort to give the greatest possible preciseness to their descriptions of individual forms. It lay therefore in the nature of the case, that those groups which we call genera and species should first be cleared up, and we find in fact at the end of this period in Kaspar Bauhin the genera already distinguished by names, if not by characters; the species by names and characters. Together with these smaller groups, many more comprehensive ones, which we now designate families, were also marked off and supplied with names, which are still in use. The 16th century established the groups and names of Coniferae, Umbelliferae, Verticillatae (Labiatae), Capillares (Ferns), and others. It is true that the determination of the limits of these groups by distinct marks was not yet attempted, but the plants belonging to these groups were again and again treated of in special chapters or ranged in due succession one after another. But as long as this was done to