Special Functions and Relations 179 



Chemical effects. - - Lime is almost as important through 

 its action in rendering the soil environment chemically 

 favorable as in its specific roles in cell metabolism. Soils 

 in which vegetation is growing have, in general, a tendency 

 to develop the condition fittingly termed acidity. When 

 the acidity increases beyond a certain point, it may become 

 extremely inhibitory to the proper growth of a variety of 

 agricultural plants, and lime, either as carbonate or as 

 slaked lime, is necessary in order to neutralize this condi- 

 tion. The carbonate of lime is less injurious and more 

 generally applicable in large quantities. 



The ecological relation of plants to soils containing 

 much or little lime is particularly interesting, and has been 

 extensively studied from the standpoint of the adaptability 

 of crops and of the distribution of wild plants as well. 

 Upon the crop side Wheeler has contributed excellent data. 

 In general, the experiments indicate that when the soils 

 show a marked acid tendency, liming is beneficial. 



Some of the plants to which the greatest benefit accrues 

 are such as lettuce, beet, onion, and cantaloup. Again, 

 crops such as cranberry, watermelon, red-top, cow-pea, 

 and others may be favorably influenced when the acidity 

 is considerable. The great majority of crops occupy an 

 intermediate position, many responding satisfactorily 

 under field conditions to moderate liming. Upon some 

 Rhode Island soils the yield of sugar-beets has been in- 

 creased by liming up to one hundred fold. Liming will 

 also affect, within the season, the character of the weeds 

 or native vegetation. It is of interest to note that closely 

 related plants are differently affected ; thus the watermelon 

 and the muskmelon, or red-top and timothy, may be 



