THE VEGETATION OF MOXTAUK 



79 



This upper layer, humus infested as it always must be, even in the 

 worst sites, is the soil as it has been affected by the decomposition of suc- 

 cessive generations of plants that have gone before, — again in the jargon 

 of the gardeners, the topsoil. 



Figure 28. (a) Subsoil under the Hither Woods; 17% fine sand and silt, 8,^% coarse 

 sand, (b) Subsoil under wooded kettlehole; 90% of fine sand, 10% silt, (c) Subsoil 

 under Point Woods; 68% coarse light sand, 32% fine light yellow sand and silt. 



On the Downs this surface soil, often of varying thickness depending on 

 the slope, is usually made up of much the same basic material as the mineral 

 soil under it, but as Fig. 29 shows, with a pretty large proportion of humus 

 in it. In the case of the surface soil under the woods, the same general 

 proposition holds true, with the exception of the surface soil under the 

 woods at Montauk Point. See figure 30. 



These purely mechanical features of the soil are perhaps best measured, 

 so far as their effects upon the vegetation are concerned, by the Hilgard* 



*See Hilgard, E. W. Soils, Chapter IX, pp. 188-266, on "The Water of Soils," 

 1919. Also "The Wilting Coefficient for Different Plants and its Indirect Determination," 

 by L. J. Briggs and H. L. Shantz, Bull. Bur. Plant Industry 230: 1-83. 1912. 



