336 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



Gulf Hammock region.* The percentages of Leguminosae are both very low, 

 probably for the same reason as in regions 9, 10 (middle division), 15 and 16: 

 namelj', the proximity of the ground-water level to the surface. But the Legum- 

 inosae are over twice as abundant in the eastern division as in the western, 

 perhaps for the same reason that the Ericaceae are less so, for a high percentage 

 of the one often goes with a low percentage of the other. 



Weeds are comparatively scarce here as yet, a natural consequence of the 

 limited development of agriculture, pointed out below. 



Economic Features — Lumbering, turpentining and grazing 

 have been the leading industries here, as in most other parts of 

 Florida, but they are being gradually superseded by agriculture. The 

 level topography has favored logging operations, and the best pines 

 have been removed, leaving some rather desolate landscapes. But 

 the long-leaf and slash pines reproduce themselves very well in 

 this kind of country, and will doubtless continue to do so until near- 

 ly all the upland is occupied by farms. 



I In 19 10 the western part had not over 14% of improved land, 

 and less than 20 inhabitants per square mile, 59.6% of them white. 

 The population increased 12.4% in the decade immediately preced- 

 ing. The eastern part had between 2 and 3% of improved land, 

 and nearly 34 inhabitants to the square mile. But counting out the 

 city of Jacksonville, which owes its development to its excellent 

 transportation facilities, and trade with all parts of the State, rather 

 than to the natural resources of the surrounding flatwoods, there 

 were only 16.2 inhabitants to the square mile in the eastern divis- 

 ion; and outside of Duval County only 14.3. The increase of popu- 

 lation between 1900 and 1910 was for the whole eastern division 

 76%, but outside of Jacksonville only 30%, and' outside of Duval 

 County 26%. (Even the last figure is above the average, though). 

 jAbout 53% of the inhabitants, with or without Duval County, are 

 white. 



At first thought it seems strange that the eastern part of the 

 flatwoods, with its apparently more calcareous soils, should have so 



*0n the Florida Keys, where the rock is all limestone, with little or no 

 soil on top of it, no Ericaceae at all have been found. 



The observation of the aversion of Ericaceae to calcareous soils is nothing 

 new (see Hilgard, Soils 522. 1906; Science II. 27:140-143. 1908; Coville, U. S. 

 Dept. Agr. Bur. Plant Industry, Bull. 193. 1911), but most persons who have 

 made such correlations before have regarded lime (or calcium) as the most im- 

 portant factor in soils, and hardly considered potassium at all. It is possible that 

 phosphorus is just as inimical to the Ericaceae as calcium is, for some parts 

 of northern Florida which have few Ericaceae are known to have decidedly 

 phosphatic soils. 



