Floristic Regions of the World by A. Takhtajan presents a widely accepted schema of biogeographical areas defined by environmental factors and floristic composition. It is a hierarchical schema that recognizes six floristic kingdoms, 35 floristic regions and 152 floristic provinces.
This schema was endorsed as TDWG standard around 1990
Takhtajan, A. 1986. Floristic Regions of the World. University of California Press. Berkeley, Los Angeles, London. xxii, 522 pp., 4 maps. ISBN:0520040279