176 FLORIDA GEOLOGICAL SURNEV SLxTH AXXUAL REPORT. 



is not specially concerned with plant associations, which are more 

 the province of the plant sociologist and ecologist. 



This meth(;d of lumping together all the plants of each region 

 is analogous to that of the chemist who in analyzing a rock contain- 

 ing a mixture of several minerals grinds it all up and detemiines 

 the composition of the whole, regardless of the separate minerals. 

 The work of the plant sociologist is analogous to that of the miner- 

 alogist who might take the same rock and identify the minerals in 

 it, and then analyze each mineral separately. The present paper 

 seems to be the hrst attempt that has been made to analyze quanti- 

 tatively the veg'etation (including shrubs and herbs as well as trees) 

 of so large an area, and no doubt there is considerable room for 

 improvement in the methods used. 



The methods here employed in making quantitative analyses of 

 vegetation are described below, for the benefit of persons who may 

 wish to test them in the same area, or to do similar work in other 

 parts of the country. 



cases it appears that the avaihil:)ility of the potassium compounds is restricted 

 by some unfavorable condition, such as cold in the far north, aridity in 

 some of the western states, and perpetual saturation of the soil in estuarine 

 swamps.) 



The soils of the "Yazoo Delta" of Mississippi contain from 0.25 to 0.91 per 

 cent of potassium, according to Hilgard, and in that whole area of over 7,000 square 

 miles there are practically no evergreens. Somewhat similar conditions exist 

 in Indiana. Illinois, the western parts of Kentucky and Tennessee, and a good 

 deal of contiguous territory. On the other hand, all the available analyses 

 indicate that potassium is less abundant in the Atlantic coastal plain than in 

 the regions of older formations, and evergreens are more abundant there 

 than in any other part of the eastern United States. 



Potassium is said to be notably deficient in peat, the world over, and 

 rather scarce in tropical soils: and the abundance of evergreens in peat l)ogs 

 and in the tropics is well known. Epiphytes (air-plants') Jiave access to no 

 potassium, or other mineral substances, except in tlie form of dust, and they 

 are all evergreen. It seems, therefore, that the proportion of ever- 



green and deciduous trees in a given region or forest is a pretty 

 good indication of the amount of available potassium compounds (commonly 

 spoken of as potash) in the soil : and of course it is the number and size of 

 the individuals rather than the number of species that counts. 



There is a widespread belief that calcium ("commonly expressed in terms 

 of lime) is the most important factor in soil fertility: but however that may 

 be, it does not seem to bear' any definite relation to evergreens. This belief 

 ^originated long before the days of chemical analyses, liecause calcareous soils 

 are usually recognizable at sight, while the presence of potassium can be demon- 

 strated only by a rather laborious analysis. The average Florida soil seems to 



