34 MASSACHUSETTS HORTICULTURAL SOCIETY 



somewhere a height near the surface water the growth of marginal 

 amphibious plants and following th'em a floating mat of herbaceous 

 plants is made possible. Gradually this gives rise to a more or less 

 continuous upper stratum of fibrous, felty or matted peat, later 

 covering nearly the entire surface of the basin. The plants of 

 the same association remain together and they become buried at 

 about the same time, as a layer essentially intact. Another change 

 in texture, structure, and composition of materials takes place when 

 after sufficient settling and firmness, the accumulation of peat con- 

 tinues above the water table by the growth of ericaceous and other 

 plants, commonly known as bog xerophytes. This type of peat 

 material contains, as a layer, woody and leafy components unlike 

 in their resistance to disintegration and dominant among which are 

 certain waxy and resinous bodies. As the conditions which favor 

 more effective weathering, and the action of bacteria and fungi 

 improve in duration as well, they begin to support the growth of 

 coniferous trees, or of a mixed forest, and later a deciduous meso- 

 phytic forest vegetation. 



The organic debris is then chiefly formed from leaf fall and con- 

 tains considerable amounts of soluble mineral matter brought to the 

 surface by the activity of the roots of trees. Moreover the trees 

 and shrubs contribute by their weight to a further sinking of the 

 underlying fibrous mat; and by their shade the displacement of 

 any surface herbaceous and ericaceous meadow-forms soon follows. 

 Thus a more woody layer of peat makes its appearance, partly from 

 windfallen timber, which takes on a granular texture as periods of 

 drought and changes in the level of the ground water table permit 

 the disintegrating and weathering processes to reach greater depths. 

 Bearing in mind the great variety of topographic and other field 

 conditions, which bring about fluctuations in the vegetation cover, 

 or in drifted and in windfallen material, it is easily seen that many 

 changes in peat layers and in their intergradations exist, so that it 

 is not always possible to assign a given peat land and the series of 

 its layers to any definite category of causal factors. Hence a 

 careful study of the conditions which exist or may ensue as a result, 

 for example of the depth, the number or character of drains, is one 

 of greater importance than appears at first sight. 



The main points, however, bearing on crop p^oducti^'ity of peat 

 lands are the following: 



