phytogeography

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The study of the geographic distribution of plants.

from The Century Dictionary.

• noun Phytogeography in its unqualified sense is plant-geography, the science of the topical distribution of plants. In this aspect it is purely descriptive, noting the locations in which a species occurs and the merely historical reason for its being there; that is, it answers the questions whether the plant is indigenous or introduced, and if the latter, whence. At this stage also the habitat (that is, the particular sort of situation in which a species grows, as mountain, bog, or seaside) is recorded; but that in the nature of the plant which determines it to its particular station is not yet investigated. Though the abundance or scarcity of a species may be noted, the interest is here in species rather than in individuals or masses, and accordingly the subject-matter of the science is the flora of the earth or of a region, the plant-content of an area taxonomically considered. Plant-taxonomy—based on morphology, which yields the natural system (which see, under natural)—is a prerequisite of plant-geography, since nothing can be said of the distribution of plants until they are separated into kinds recognizable by constant characters. The science as thus limited has in recent times (by Warming and others) been denominated floristic plant-geography or floristics, in contrast with œcological phytogeography (which see). Historically and in natural order of thought the floristic view is first, being represented by numerous floras, by the descriptions of botanical travelers, and by more systematic accounts which pass into the later point of view.
• noun The geography or geographical distribution of plants: correlated with zoögeography.

from the GNU version of the Collaborative International Dictionary of English.

• noun The geographical distribution of plants.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun biology The science that studies the geographical distribution of plants; geobotany