MARYLAND WEATHER SERVICE 147 



of water so tenaciously that the plants growing in it often suffer 

 drought when there is an abundance of water within very short 

 distance but very firmly held by the capillarity of the fine soil. 

 The Loblolly is, in other words found most abundantly in the soils 

 which are subject to the greatest fluctuations of soil moisture content. 



The feature of change in shore line topography which has the 

 greatest mass effect upon vegetation is that of the filling in of 

 coves and bays and the narrowing of estuaries. The deposition of 

 silt in the marshes has increased greatly since the cultivation of the 

 Upland incident to the settling of the country, and has tended to 

 obscure the real trend of change. The upbuilding of Marshes in- 

 variably leads to the entrance of the Stream Swamp flora, some of 

 the herbaceous members of which are already present in the Marshes. 

 Acer rubrum is the first of the trees to enter the Marsh formation, 

 as it does repeatedly for many years before the conditions are fa- 

 vorable for the development of the trees beyond the seedling stage. 

 The upbuilding of shoals gives opportunity for the encroachment of 

 the Marsh vegetation on the waters, which is taking place to a 

 limited extent. The foi-emost plant in this advance is Spartina 

 stricta var. maritima. Where the upbuilding is rapid and due to 

 the action of currents rather than to the slow deposition of mud 

 from muddy water, the soil is coarser and is raised to a level such 

 that it is well drained. This process gives rise to sand bars or 

 spits which maintain a xerophilous vegetation and develop a forest 

 covering much more directly and rapidly than do the newly up- 

 built Marshes, as has been described for several localities in Chesa- 

 peake Bay. 



Geological evidence shows that the Eastern Shore is at present 

 undergoing a slow subsidence, the end effect of which will be to 

 offset the upbuilding of marshes, if not to actually increase the 

 areas of marshland, causing them to encroach on the Upland. At 

 two localities on the inner edge of the extensive marshes of Dor- 

 chester County the writer saw unmistakable evidence of the en- 

 croachment of the Fresh Marsh upon forests of Pinns iaeda. These 

 localities are where the Upland behind them is very flat for many 

 miles. The slight erosion from this very stretch of country is 



