244 



If the figures for each species in each division of the foregoing 

 list are added together they will form approximately a geometrical 

 progression. Whether there is any explanation for it or not, 

 this seems to be a fundamental property of quantitative analyses 

 of vegetation, as it is of many other kinds of statistics (e. g., the 

 populations of the cities of the United States, arranged in order 

 of size.) 



If the trip had been made a few weeks earlier or later Cornus 

 fiorida and Cercis Canadensis would have stood considerably 

 lower in the list of trees, because at this time they were in bloom, 

 and therefore very conspicuous. (The fact that Cercis was seen 

 56 times north of Knoxville and only three times south of there 

 indicates that its flowering season was just about at an end in 

 that latitude.) The numbers for most of the oaks would have 

 been higher in summer, for it was difficult to identify them with 

 their leaves only partly developed. 



If we add together all the figures for evergreen trees (nine 

 species, all conifers) we find that they make up 39.2 per cent, of 

 the total number of trees; and this estimate is probably not 

 affected much by the season at which the observations were made. 

 Doing the same thing for each column of figures separately, we 

 get 34 per cent, of evergreens for the Virginia portion of the route, 

 45.1 per cent, for Bristol to Knoxville, 47 per cent, for Knoxville 

 to Chattanooga, and 35.2 per cent, for the Alabama portion. 

 (My estimate for the whole Coosa valley region of Alabama, in 

 the publication above referred to, is 40 per cent.) Just why the 

 percentage of evergreens should be so much higher in the valley 

 of East Tennessee than in the corresponding parts of Virginia 

 and Alabama is not at present obvious. The discrepancy can 

 hardly be due to errors of observation, for the work was done 

 under the same conditions all the way; and it is probably not 

 correlated with any phaenological or climatic factors, because the 

 Tennessee figures do not lie between those for Virginia and Ala- 

 bama. The fundamental cause is probably in the soil. 



The distribution of the following species is of more than passing 

 interest. 



Pinus Taeda was first seen a little north of Cleveland, Tenn., 



