- [Footnote: employed in the work entitled Regni vegetabilis Systema
naturale (T. i. p. 128, 396, 439, 464, and 510), and Kunth has carried it out in regard to the whole number of species of Compositæ at present known (above 3300). It does not show which is the predominant family either in the number of species or in the quantity of individuals as compared with other families; it merely tells how many of the species of one and the same family are indigenous in each country or each quarter of the world. The results of this method are on the whole more exact, because they are obtained by the careful study of single families without the necessity of being acquainted with the whole number of the phanerogamæ belonging to each country. The most varied forms of Ferns, for example, are found between the tropics; it is there, in the tempered heat of moist and shaded places in mountainous islands, that each genus presents the largest number of species: this variety of species in each genus diminishes in passing from the tropical to the temperate zone, and decreases still farther in approaching nearer to the pole. Nevertheless, as in the cold zone—in Lapland, for example—those plants succeed best which can best resist the cold, so the species of Ferns, although the absolute number is less than in France or Germany, are yet relatively more numerous than in those countries; i. e. their number bears a greater proportion to the sum total of all the phanerogamous plants of the country. These proportions or ratios, given as above-*mentioned by quotients, are in France and Germany 1/73 and 1/71, and in Lapland 1/25. I published numerical ratios of]*
