274 THE PLANT LIFE OF MARYLAND 



become deep or retentive of moisture. The forests comprise two 

 groups, according to the drainage conditions: (1) That on steep 

 slopes, dominated by Pitch Pine and Chestnut Oak, with an abun- 

 dant undergrowth of such dry ground vegetation as the Wild Indigo. 

 (2) That of more gentle slopes, the White Oak becomes prominent, 

 and the soil deeper and more valuable for all purposes. These soils 

 wash badly, and are on this account best in their natural condition 

 of forest. When the trees have been removed the poor quality of the 

 soil for farming purposes brings it back to a condition for reforest- 

 ing in a few years. 



The conditions of plant growth and distribution in the Upper 

 Province of the Midland Zone are less different in the several natural 

 divisions into which the topography divides the region than might 

 have been expected. This uniformity seems to be produced by the 

 repetition of the same general conditions at intervals within the area, 

 and to the comparatively slight change in elevation and rainfall 

 between the eastern and the western members of similar types of soil 

 or topographic conditions. Thus the valleys rise from 190 feet above 

 tide at the mouth of the Monocacy, near the eastern limit of the dis- 

 trict to 610 feet at the mouth of Wills Creek, close to its western 

 limit, a rise of only 420 feet in the 148 miles or about the same 

 difference as that between the Gunpowder Eiver at Loch Raven 

 (near the dam), and the head of Beaverdam Run on the east slope 

 of Chestnut Ridge, west of Cockeysville, a distance of a dozen miles. 



The differences in elevation between the bounding ridges is of the 

 same gentle character, Parr's Ridge, at Westminster, being about 

 1000 feet above tide, and Wills Mountain 1690 feet above the bed of 

 Wills Creek, near Cumberland, a difference of about 700 feet in the 

 distance between the limits of the area considered. When similar 

 soil or topographic conditions are repeated within the limits of so 

 small variations, there is not a great deal of change needed on the 

 part of the vegetation to keep pace with any differences that may 

 locally modify the general type of habitat. The presence of a spring 

 may produce more difference in the space of a dozen rods about its 

 opening, than the broader conditions give in the greater area included 

 in this discussion. 



