FREE INSTITUTE OF SCIENCE 



VEGETATION OF SOUTH FLORIDA 



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species representing the family Leguminosae would be respectively 41 genera 

 and 71 species. In these 24 families, including over 5 species of plants in 

 each family, are included 572 species out of a total flora of 878 species, or over 

 one-half of the whole number of species. 



Generic Coefficient. The proportion of genera to species in a flora is known 

 as the generic coefficient. The generic coefficient of the whole Miami flora is 

 obtained as follows : 



878 : 522 :: 100 :x, where x becomes 59.4%. The generic coefficient of the 

 flora of the Florida keys is obtained likewise by the proportion: 



627 :4o8 ::ioo :x, where x = 6s%. 



If we exclude from the total number of genera and species the introduced 

 ones, our total numbers stand for the Miami flora 796 species and 460 genera, 

 and for the flora of the Florida keys 533 species and 346 genera. The generic 

 coefficients would then stand for the Miami flora as 58.5% and for the flora 

 of the Florida keys 64.9%, approximately in both estimations 59% and 65%. 

 If we arrange this information in a table, we have : 



The figures of this table are a direct confirmation of Jaccard's lawf 

 of plant distribution that "the Generic Coefficient is inversely proportional to 

 the diversity of the ecologic conditions. " Such regions as the central and 

 northeastern United States (Gray's Manual); southeastern United States 

 (Small's Flora); Rocky Mountains (Nelson's Manual); British Islands 

 (Druce) and Switzerland have ecologic conditions of the greatest diversity, and 

 hence low generic coefficients, while the Miami region, that of the Florida 

 keys and the pine-barren region of New Jersey with fairly uniform physical 

 character have relatively high generic coefficients. 



Coefficient of Community. Some emphasis has been placed by European 



* See Harper, R. M.: Ann. N. Y. Acad. Sci. 17: 323. 



\Jaccard, Paul: Nouvelles Recherches sur la Distribution Florale. Bull. Soc. Vaud. des Sci. 

 Nat., xliv: 259, 1908. 



