BOTANY. That division of biological geography that deal: with the distribution and with the cause: of distribution of plants. The subject has been studied since the time of Linnaeus, but its modern period dates from the works of Al phonse De Candolle and of Crisebach, about the middle the century. :\lore recently. the works id \Vanning. Drink, Engler. and Schimper have added much to our knowledge of the subject. Phytogolgraphy may be divided into two main heads: First, ecological phytogeog raptly. whiell seeks to account for the distribu tion of plant-forms Ig. g. the forms peeuliar to wat•r-plants, to desert-plants, etc.! and the causes, mainly climatic and meteorological, of such distribution; second, floristic phytogeog raphy, which has for it, aim the subdivision Df the world into floral regions and districts. and the study of the distribution of Ida n I -sperics in these region:, thus dealing with the species as units, and seeking to determine the geological and similar valises for plant distribution.
Schimper subdivides the world into tropical, temperate. and frigid regions, alpine districts, and the seas. Each of these divisions, especially the first two, is in turn redivided into forma tion:. These formations, if determined by cli matic factors. ate termed climatic formation:, if by local or soil factors. edaphic formation:. For desert, and tropical rainy forest: are climatic formations. their existence being determined mainly by the distribution of atmos pherie moisture; on the other hand. the flora of a s\vanip or of a heath. being governed mainly by local soil factors, is spoken of as an edaphie format ion.