38 ECONOMIC BOTANY OF ALABAMA 



fertility of the soil.* Although the map is s^eneralized and not abso- 

 lutely accurate, it would he difficult to improve on it without map- 

 ping the location of every cotton field, and even that would not 

 mean much at present, since the use of fertilizers has extended the 

 cotton area in the poorer regions and the boll weevil has reduced it 

 in the black belt. 



This ma]) shows some striking correlations with the regional 

 map. and with the distribution of many trees and shrubs, as can be 

 seen by comparing it with the distribution maps of Finns palustris, 

 Illiciiiin, CyriHa, Ilex glabra, and OsiiiantJuis. Similar correlations 

 are mentioned at several places in the text. 



The three climatic maps are taken from Dr. Smith's report 

 for 1881-2, which deals with the agricultural features of the state. 

 More accurate ones could be constructed by taking advantage of 

 the weather records of the last four or five decades, but these 

 illustrate the general tendencies remarkably well considering their 

 age. and as the publication in which they originally appeared has 

 long been out of [)rint, it seems desirable to perpetuate them in this 

 way. 



The map showing average annual temperatiu'e needs little com- 

 ment, except to note that temperature is probably a limiting factor 

 in the case of many species confined to the extreme north or south 

 of the state. Details for several weather stations can be found in 

 Monograph 8 (page 188). 



The two seasonal precipitation maps are rather significant. 

 They show the total amount of rain falling in the three winter 

 months (December to February) and in the three summer months 

 (June to August). The ratio of winter or summer to annual pre- 

 cipitation might be better, as suggested in Monograph 8 (pp. 19, 

 24).t but it is very iriteresting to note that the most fertile regions 

 have the most rain in winter, while the ])rincipal long-leaf pine 

 region has the heaviest summer rain in the western part, and the 

 least winter rain in the eastern part. 



*One important exception to the correlation between cotton and soil fer- 

 tility is the Mobile delta, which has very fertile soil, but is very little culti- 

 vated on account of being subject to inundation. 



tSee also Science II. 48:208-211. Aug. 30, 1918. 



