coville: formation of leafmold 81 



As the decomposition of such leaves progresses the acid sub- 

 stances are disorganized and largely dissipated in the form of 

 gases and liquids, while the lime being only slightly soluble 

 remains with the residue of decomposition, the black leafmold, 

 and renders it alkaline. 



In soils poor in lime, trees and other plants constituting the 

 vegetative mantle of the earth may be regarded as machines for 

 concentrating lime at the surface of the ground. This lime is 

 drawn up by the roots in dilute solution from lower depths, is 

 concentrated in the foliage, and the concentrate is transferred to 

 the ground by the fall and decomposition of the leaves. The 

 proverbial agricultural fertility of the virgin timberlands of our 

 country was undoubtedly due in large part to the lime accum- 

 ulated on the forest floor by the trees in preceding centuries, and 

 to the consequent alkalinity of such surface soils when the tim- 

 ber had been removed and the leaf litter was thoroly decomposed. 

 After a generation or two of reckless removal of crops the surface 

 accumulation of lime was depleted and unless. the underlying soil 

 was naturally calcareous a condition of infertility ensued which 

 for the purposes of ordinary agriculture could be remedied only 

 by the artificial application of lime. 



The chief agents in the decay of leaves are undoubtedly fungi 

 and bacteria. There are other agencies, however, that contribute 

 greatly to the rapidity of decay. Important among these are 

 earthworms, larvae of flies and beetles, and myriapods or thou- 

 sand-legged worms. Animals of all these groups exist in myriads 

 in the leaf litter. They eat the leaves, grind them, partially 

 decompose them in the process of digestion, and restore them 

 again to the soil, well prepared for the further decomposing 

 action of the microscopic organisms of decay. 



The importance of earthworms in hastening the decay of veg- 

 etal matter was pointed out long ago by Darwin in his classical 

 studies on that subject. The importance of myriapods, however, 

 as contributing to the formation of leafmold has not been ade- 

 quately recognized. In the canyon of the Potomac River, above 

 Washington, on the steeper forested talus slopes, especially those 

 facing northward, the formation of alkaline leafmold is in active 



