MARYLAND WEATHER SERVICE 213 



less abundant than on the Loams, and the Chestnut Oak and Scarlet 

 Oak are nearly absent. The Tulip Tree, on the other hand, is 

 quite as abundant as on the Soil-covered Slopes of the Loam soils, 

 and the White Oak is only slightly less so. The Swamp Oak is 

 more abundant than on the Loam slopes, and the Black Walnut, 

 Linden and Ked Bud are infrequent. The herbaceous species which 

 arc rare or absent on the gabbro clay are such as the species of 

 Meibomia, Lespedeza, Lccliea and lldiantliemum, Mitchella 

 repenSj Epigaea repens and other of the commoner psammophilous 

 plants. 



Vegetation of the Serpentine Barrens. 



The Serpentine Barrens of the Lower Midland District have 

 been examined at Conowingo in Cecil County, Dublin in Harford 

 County, the Bare Hills and Soldier's Delight in Baltimore County, 

 and near Gaithersburg in Montgomery County. The principal 

 features of the Barrens are extremely uniform in all of the areas, 

 and like the Gravel they are most pronounced in the character, 

 of their vegetation on the topland and in the driest situations, for 

 some of the deepest Conowingo clay in Cecil County bears a group- 

 ing of forest trees and other vegetation not very unlike that on 

 Loam Slopes. The fact that the serpentine weathers readily cause 

 the rock outcrops to be covered with fragments (See Plate XX, 

 Fig. 2) and the failure in formation of a soil is possibly connected 

 not only with the ready drainage afforded by the topography, but 

 with the chemical character of the rock fragments as well. That 

 the peculiarities of the Serpentine areas are not due solely to the 

 physical conditions is attested by the difference between their veg- 

 etation and that of the shale exposures of the Upper Midland Dis- 

 trict, where the physical conditions are almost identical. That the 

 physical conditions are partly responsible, however, for the peculi- 

 arities noted is shown by the normal character of the vegetation of 

 the deep areas of Conowingo clay, where, on the other hand, it is 

 altogether likely that much of the harmful excess of magnesium 

 has been leached out of the soil. 



Some of the Barrens are of the same physiognomy as other 

 forests in the Midland Zone, but those in the Soldier's Delight 



