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FREE INSTITUTE OF SGIENGE 
VEGETATION OF SOUTH FLORIDA 
183 
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 :: TOO: x, where x becomes 59.4%. The generic coefficient of the 
flora of the Florida keys is obtained likewise by the proportion: 
627 :408 ::100:x, where x=65%. 
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: 
REGION SPECIES GENERA GENERIC COEFFICIENT 
e ран 796 466 59% 
ТОРО Es S oA AT Es mr 533 346 65% 
eee, утех 555 250 45% 
Altamaha Grit Region of Georgia * 797 404 50% 
Southeastern United States....... | 6364 1494 23% 
Region of Gray’s Manual. ........ 3413 821 24% 
Central Rocky Mountains........ 2733 649 24% 
British Flora (Druce) including 
A ee ne 2964 734 24% 
Wee!!! US. 2453 659 27% 
The figures of this table are a direct confirmation of Jaccard's law ї 
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. 
1 Jaccard, Paul: Nouvelles Recherches sur la Distribution Florale. Bull. Soc. Vaud. des Sci. 
Nat., xliv: 259, 1908, 
