MARYLAND WEATHER SERVICE 201 



occur in irregular and scattered areas along the edge of the District 

 that is bounded by the "Fall-line" are usually in the form of homo- 

 geneous beds of gravel, or in some localities are lacking in boulders 

 and pebbles, possessing a fine clay texture, — the Susquehanna clay 

 of the Soil Survey. The vegetation of the Susquehanna gravel and 

 the Susquehanna clay is almost as marked as that of the Serpentine 

 Barrens, particularly on the hills. It is notable that the Lower 

 Midland District contains no outcroppings of shale or sandstone, 

 which are the two commonest underlying rocks throughout the Upper 

 Midland District and the Mountain Zone. 



The dominant natural vegetation of the Lover Midland District 

 is a deciduous forest, in which, on the loam soils, the characteristic 

 trees are the Chestnut, the Elack Oak, the White Oak, the Chestnut 

 Oak, the Scarlet Oak, the Mockernut Hickory, and the Pignut Hick- 

 ory. In all of the deeper loam soils, particularly on lower slopes, 

 there are numerous tree species in addition to the above, among 

 which the Tulip Tree, the Beech, the Bed Maple, the Bitternut 

 Hickory, the Black Walnut and the Black Gum are prominent. In 

 the Flood Plains there are additional species, as the Swamp Oak, 

 the River Birch, the White Ash, the White Willow and the Horn- 

 beam. The coniferous trees are but five in number, — the Hem- 

 lock, the White Pine, the Pitch Pine, the Scrub Pine and the Red 

 Cedar, of which the last two are the only common species. Pure 

 stands of Scrub Pine are frequently to be met with on upper slopes, 

 but are usually young, and seem merely to represent the earliest 

 stage in the reforestation of areas formerly occupied by deciduous 

 forest. On many very steep rocky slopes, however, the Scrub Pine 

 is to be found on what is apparently a natural habitat for it. The 

 Pitch Pine is occasional in its occurrence throughout the District, 

 but is seldom abundant except on the gravel and clay areas of the 

 Cretaceous deposits. The Hemlock and White Pine are confined 

 to rocky ravine slopes, where they were much more abundant in 

 the virgin condition of the country. The Red Cedar, although now 

 widespread, is found naturally only on the Serpentine Barrens and 

 very steep rocky slopes. 



The Cecil clay forests are somewhat different in composition from 

 those of the loams, although the same species are involved in their 



