350 



this even seems to be needed in considerable quantity, judging from 

 the extensive leaf-surface from which evaporation is carried on. 

 Aqueous vapour in the air, as suggested by Dr. Royle, and abundant 

 hygroscopic moisture in the soil itself, as I would add, seem to be 

 decidedly the sources from which this requirement is to be met. 



The great advantage derivable from a soil of high capacity for ab- 

 sorbing and retaining moisture will be, that it will enable the plant 

 to withstand vicissitudes of weather and season ; in damp weather 

 hygroscopic water will be condensed, to be stored up in the retentive 

 soil until required in the midst of drought ; in August or September, 

 when seed and fibre are to be formed, and when therefore diminished 

 leaf-activity is desirable, the roots will gradually draw up a supply of 

 this water, limited*, but sufficient to maintain healthy life. 



These remarks no doubt apply also to the absorption of gases, and 

 of mineral matter withdrawn from solution, as has been noticed in a 

 previous part of the paper. The power of steadily accumulating and 

 gradually dispersing seems to be one of the well-marked and beau- 

 tiful provisions of the " economy of nature." 



The soil of the prairie region of central Alabama fulfils the above 

 conditions admirably, and to this fact should, I believe, be in large 

 measure attributed the success with which cotton is cultivated upon it. 



To sum up the results of the examination of this fertile cotton soil, 

 it is shown to be a stiff aluminous clay, containing moderate amounts 

 of organic matter and of the mineral substances needed by the plant 

 as food of great uniformity, and in an exceedingly fine state of 

 division above all, possessing a very high capacity for absorbing and 

 retaining heat, moisture, gases, and soluble mineral matter. 



APPENDIX. 



Mechanical Treatment of Cotton-soil, as practised in Alabama. 



In order to complete the subject of Alabama cotton-soil, it seems 

 desirable that to the preceding results should be added a brief state- 



* The porous chalky substance referred to as " rotten limestone," which under- 

 lies the soil of the cane-brake, has itself very similar capillary and absorptive 

 power ; it is penetrated by sandy strata, through which water can readily flow, 

 and hence it is not at all inconceivable that supplies of moisture may even through 

 this be drawn up from the depth of 20 or 30 feet, at which the first sandy bed is 

 often met. 



