202 THE PLANT LIFE OF MARYLAND 



make-up. The Chestnut Oak is very rare and the White Oak, the 

 Tulip Tree and the Swamp Oak are much more abundant on the 

 topland here than they are on the loam. The Serpentine Barrens 

 are occupied almost solely by an open stand of Black Jack Oak, 

 Post Oak and Red Cedar, although some of the commoner trees of 

 the loams and clay occur on the deeper areas of Conowingo clay. 

 The gravel and clay soils of the Cretaceous deposits are character- 

 ized by a forest of Chestnut and Chestnut Oak, with an accompani- 

 ment of xerophilous shrubs and herbs. 



A comparison of the soil-covered slopes along Deer Creek in Har- 

 ford County, on the loam soils in the vicinity of Glenville and on 

 the Clay in the vicinity of Kalmia showed the topography to out- 

 weigh the soil as a factor in determining the make-up of the vegeta- 

 tion. Even on the Serpentine Barrens the topography plays an im- 

 portant part in bringing the vegetation of the lower slopes to a 

 character more nearly approaching that of the lower slopes of the 

 other soil types than that of the thin-soiled topland of the Barrens. 

 On the gravel the influence of topography is considerable, but not 

 so great as on the Serpentine ; the lower slopes of Gravel hills are 

 not closely related in flora to the lower slopes on the other soil 

 types. 



The fact that the vegetation of the soil-covered slopes, as well as 

 of rock outcrops and flood plains is identical on the loams and on 

 Cecil clay will make it unnecessary to treat these features separately 

 for the clay. 



Vegetation of the Loam. 



topland. 



There is no remaining virgin forest in the Lower Midland District 

 and the bulk of the woodland is in small tracts scattered through a 

 highly cultivated farming country. The steepness of many hillsides 

 is responsible for their having been left in timber, and the Serpen- 

 tine Barrens and Gravel hills have not been cultivated on account 

 of the poverty of their soils. On a few old estates there are bodies 

 of timber that have been undisturbed for half a century, a lapse 

 of time which has enabled the trees to attain to a splendid size but 



