MARYLAND WEATHER SERVICE 219 



over a period of time in winch erustal movements or climatic 

 changes may have opportunity to offset the influence of topography. 



In the entire Midland District the topland presents differences 

 of vegetation which are due to the character of the underlying 

 rock. These differences were doubtless more pronounced in younger 

 states of the topography than they are now, but they are such that 

 they will always manifest themselves even if the region were to 

 undergo complete planation. 



The Topland vegetation of a particular soil type is that which 

 must be looked upon as the climax, for it is the type which has 

 resulted from the maturing of the topography. The Rocky Slopes 

 arc but a trifling percentage of the total area of the District, and 

 are due to secondary lateral cutting by the larger streams, i. e., a fea- 

 ture due to a regression in the topographic development of the Dis- 

 trict. The Rocky Slopes, however, are destined to pass through the 

 Soil-covered Slope stage ultimately to that of the Topland. The 

 Flood Plains are likewise destined to silt up until their vegetation 

 approaches in character that of the Topland. 



