336 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1913. 



Whence comes the abundance of lime in an alkaline, richly cal- 

 careous leafmold formed over a soil distinguished by an actual 

 poverty of calcareous matter? 



If the leafmold is rich in lime the leaves from which it is derived 

 should also be rich in lime. A determination of the amount of cal- 

 cium oxid in the dried freshly fallen leaves of some of our well- 

 known trees shows this to be true, as illustrated by the following 

 selections : ^ 



Per cent of 

 Kind of leaves. calcium oxid. 



Red oak {Quercus rubra) 1.73 



Silver maple {Acer saccharin um) 1.88 



Pin oak (Quercus palustris) 1.91 



Sweet gum (Liquidambar styraciflua) 1.92 



Bur oak {Quercus macrocarpa) 2.39 



Elm {Vlmus americana) 2.50 



Sugar maple {Acer saccharum) ^ 2.56 



Tulip tree {Liriodendron tulipifera) 2.84 



Hickory {Hicoria myristicaeformis) 3. G6 



Gingko {Ginkgo Mloba) 4.38 



Basswood {Tilia americana) ■ 4.50 



Orange {Citrus aurantium) 6.77 



These analyses show that the amount of lime in the leaves of trees 

 is often astonishingly large. 



It should be understood that the lime does not exist in the leaf in 

 the form of actual calcium oxid. It is largely combined with the 

 acids of the leaf and serves in part to neutralize them, but is insuffi- 

 cient in amount to effect a complete neutralization. In all the kinds 

 of leaves and herbage thus far examined the net result is an acid 

 condition, although lime may be present in large amount. Thus in 

 the leaves of silver maple a condition of excessive acidity exists, 

 about 0.9 normal, notwithstanding the presence of nearly 2 per cent 

 of lime. 



As the decomposition of such leaves progTesses 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 vege- 

 tative mantle of the earth may be regarded as machines for concen- 

 trating lime at the surface of the ground. This lime is drawn up b}^ 

 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 



1 The lime determinations were made by Mr. J. F. Breazeale, of the Bureau of Chem- 

 istry, Department of Agriculture. 



