32 



The percentage of organic matter shows, as might be expected, 

 remarkable differences. Sample 1, which approaches primitive 

 soil, was taken from a region where deforestation has not been 

 common, and the large amount of organic matter represented here 

 is the result of years of leaf decay. The color of the surface soil 

 is black ; at eight inches below the surface it is only a trifle lighter. 

 Sample 2 presents a yellow color below the surface on account of 

 the organic matter present being slight. This sample, which sup- 

 ported a growth of inferior grasses, goldenrods, etc., presented a 

 dark color only at the surface. Sample 3 is a greenhouse soil 

 adapted to forcing crops. These soils usually contain from 8 to 

 15 per cent of organic matter to a depth of 12 to 15 inches which 

 is supplied by manure and by the decay of roots. 



Those plants which have shown the greatest tendency to become 

 rare, and in most instances are only to be found where there is 

 more or less of an approachment to primitive soil conditions, are 

 the humus-living plants, or those which depend upon organic mat- 

 ter. Not only is the number of humus-living plants decreasing, 

 but their former luxuriance is by no means the same. Certain 

 wild species of plants when grown in a soil similar to sample 1 are 

 from one-half to three times as large as those grown in soils which 

 contain a superficial layer of organic matter of a smaller percent- 

 age. There are limited areas in this State where the soil condition 

 approaches a primitive state, and in such places plant development 

 is much more luxuriant than in soils containing little organic mat- 

 ter, which is so typical of many of our present day soils. With 

 the exhaustion of the organic matter in the soil there has taken 

 place a change in its chemical and physical properties. It no 

 longer possesses the same water-retaining capacity or the same 

 amount of available plant food. In this way the floral conditions 

 have been changed, and instead of finding the characteristic species 

 of plants which once thrived in these soils we find their places taken 

 by such species as the white birch, poplar, bush clovers (Lespe- 

 dezeas), goldenrods, beard's-grass (Andropogons) , Indian grass 

 {Chrysopogon nutans), etc. 



The cause of the decrease in organic matter may be traced to 

 various operations. During the time of the early settlements of 

 Massachusetts our ancestors found here woodland containing an 

 exceptionally fine growth of trees, which constituted a forest diffi- 

 cult to penetrate. Here and there were open fields containing 

 native grasses and herbaceous plants growing luxuriantly, and our 

 large river valleys were especially noted as being free from dense 

 forest growths. This native growth exhibited a natural adapta- 

 bility subjected to the laws of natural selection, as its conformity 



