218 FLORIDA GEOLOGICAL SURVEY-I3TH ANNUAL REPORT

 CENSUS OF TIMBER TREES.
 In contrast with the great diversity of vegetation, the species of trees in central Florida are rather few. About two dozen that are widely distributed in the eastern United States reach their southern limits a little north of our area, while a much larger number of tropical species do not extend quite so far north.
 In the following table the large trees already mentioned in the regional descriptions are brought together in a single list, with a column for each region filled with symbols showing the relative abundance of each species there. The writer's observations are hardly complete enough yet to warrant assigning percentages to every species, but those over 20 are indicate d by numbers, and those under 20 by easily remembered letters corresponding to groups of percentages, as follows:10-20%, A (abundant)
 3-10%, C (common) 1-3%, F (frequent)
 0.1-1%, 0 (occasional)
 0.01-0.1%, R (rare)


 It will be noticed that these letters are in alphabetical order, so that in the table the letters nearest thebeginning of the alphabet indicate the highest percentages. Where the occurrence of a given species is probable but not proved an interrogation point is used, and where it is believed to be entirely absent the space is left blank.*
 The smaller and rarer trees are omitted, as are all the shrubs and herbs, because they are hardly important enough to justify taking up much space with them, and also because their relative abundance cannot be. determined so accurately.
 At the top of each column is given the estimated percentage of evergreens in the forests, which is believed to be pretty closely correlated with soil fertility.
 *A similar scheme was used for the trees of southern Alabama in Geol. Surv. Ala. Special Report No. ii, pp. 102-104. Aug., 1920.