Linnæus, besides, saw the necessity of bringing together all the descriptions of plants already existing, and of wording them in such a way that, without losing anything essential in the description, they should occupy the smallest possible space. Such a condensed description is now known as a diagnosis.
When he had accumulated a considerable number of diagnoses he saw that it was difficult to find one's way through them, and he set about arranging them after some of the most striking characteristics which did not necessarily indicate relationship, but were simply as a means of classification and recognition. He took for this first the number of stamens, bringing all plants with one stamen in the flower together, all with two, three, four, five, ten, etc., into their several classes, in this way creating the groups of the Monandra, Decandra, Polyandra, etc.
Having done this, he recognized that a subdivision of these groups was desirable; that many plants with the same number of stamens yet differed considerably among one another; and these smaller groups he called genus, plural genera. Such a genus now, for example, is the buttercup, which he called Ranunculus. He saw that further subdivision could take place, and that there were a great many plants which, though evidently all buttercups, yet differed sufficiently to be distinct. So he resolved to give every plant two names, the first one being the genus name, here Ranunculus, the second one expressing some property of that particular kind of Ranunculus, and thus indicating the species. Thus he found, for example, that one buttercup had an acrid taste, and he called it the acrid buttercup—in Latin, Ranuncidus acris; that another one always grew on marshy places; he called it the marsh buttercup—in Latin, Ranunculus palustris, etc.
Latin names were used simply as a matter of convenience, as it was much easier to know one Latin name than a dozen names in a dozen different languages for the same plant. Linnæus's system was consequently one of mere convenience and thoroughly artificial.
It had, however, already been recognized that certain plants belong naturally together, as grasses, for example, while Linnæus's system often placed two grasses very far apart. This conception of relationship, however, could not be expressed well before Darwin had shown that plants had not always been as they are now, but that the higher plants had gradually been developed from the lower ones. Then an entirely different system arose—a system which expressed the relation of plants in the way of a genealogical tree; this system is generally known under the name of the natural system. It is after this natural system, which expresses our conception of the blood relation between the different plants, that our present herbaria are arranged,
