151 



description of it is taken from the report of this bureau on the 

 soil survey of Tazewell county (Bonsteel, '03). 



"The sand consists of partly rounded grains of quartz stained 

 rusty yellow or orange by iron, and made slightly loamy by 

 the presence of silt or clay. There is no distinction between 

 soil and subsoil. Organic matter is very deficient, as is shown 

 in the following table giving the mechanical analysis of a sam- 

 ple of Miami fine sand from 7| miles west of Delavan, Tazewell 

 county. 



"Organic matter, 0.53% Fine sand, .25-. 1 mm., 62.20% 



Gravel, 2-1 mm., 0.10% Very fine sand, .l-.05mm., 6.24% 



Coarse sand, 1-.5 mm., 3.92% Silt, .05-005 mm., 2.86% 



Medium sand,. 5-25 mm., 22.26% Clay, .005-.0001 mm., 2.42%" 



The soil in the depressions between the sand deposits, 

 known as Miami loam, contains from 1.69% to 2.80% of organic 

 matter, while other soils in the county contain as high as 4.69%. 



In every region where large quantities of sand are exposed, 

 the wind plays an exceedingly important part in the ecology 

 of the plant life. Inland it is by no means so active a factor 

 as on or near the shores of large bodies of water, where its ve- 

 locity is greater and the sand is less protected by a covering of 

 vegetation. Sand blown by the wind may do considerable me- 

 chanical injury to the leaves, young stems, and other succulent 

 parts, but as the plants growing in the sand associations are 

 usually adapted to it they are seldom much affected. Growing 

 crops, however, are sometimes badly damaged. The native 

 plant-covering is normally sufficient to prevent much blowing, 

 but if it is any way destroyed, large excavations called blow- 

 outs are formed, which, as they increase in size, undermine and 

 destroy most of the vegetation. The sand in these blowouts 

 is so loose and easily disturbed by the wind that only a few 

 species of plants are able to grow in it. The sand removed by 

 the wind is deposited on the leeward side in a fan-shaped heap 

 nearly or quite bare of vegetation (PI. XII., Fig. 2), or is 

 blown on as a traveling dune. To protect themselves against 

 this shifting of the sand, many plants are especially adapted 

 as sand-binders, and effectually hold the sand in position. 



