If we take with Drude the number of known families of flowering plants at 240, 92 are generally dispersed, 17 are more restricted, while the remainder are either dominant in or peculiar to separate regions.
The Alps have 172 endemic species and at least 15 genera that are not found in the Pyrenees, while the latter range counts about 100 endemic species with several (six or seven) genera not found in the Alps Drude has accordingly suggested the substitution of the term High-mountain floras for Alpine, which he regards as misleading.
By P. de Tchihatchef (Paris, 1875); Engler, Versuch esner Entwicklungsgeschichte der Pflanzenwelt (Leipzig, 1879-1882); Oscar Drude, Manuel de giographie botanique, transi.
Drude, Handbuch der Pflanzengeographie; A.
The simplest classification is perhaps that of Drude according to climatic zones, subdivided according to continents.
Of nickel six P. Drude, Ann.
P. Drude has obtained a similar formula based on the electromagnetic theory, thus placing the theory of dispersion on a much more satisfactory basis.
For the theory of dispersion see P. Drude, Theory of Optics (Eng.
Drude Annalen (1908), 2 7, p. 537 and (1909), 29.
Drude, and experimental contributions from innumerable workers, such as F.