MARYLAND WEATHER SERVICE 91 



Those particular constellations of physical conditions which we 

 arc accustomed to designate by the loose term "habitats" are different 

 from each other chiefly by reason of differences in soil conditions, 

 operating directly or indirectly. The fundamental determination 

 of the soil characteristics of habitats by geology and topography and 

 by physiographic changes, gives to the most marked habitats a 

 definite geographical range. The three classes of plants of the 

 Coastal Zone of Maryland which have already been listed, those of 

 the Strand, of Salt Marshes and Pine Barrens are examples of plants 

 which are limited to the Coastal Zone in their distribution by reason 

 of the limitation of their habitats through geologic and physio- 

 graphic causes. Each of the Floristic Zones possess habitats almost. 

 as strongly marked in their physical conditions and their vegetation 

 as are the Salt Marshes and the Strand, as for example the Serpen- 

 tine Barrens of the Lower Midland District and the Swamps of the 

 Mountain Zone. In addition to these each Zone possesses many less 

 sharply marked habitats in which the physical conditions are not so 

 extreme and the vegetation not so distinctive. The Sandy Loam 

 Upland Swamps and the Sandy Stream Swamps of the Coastal Zone 

 are characterized by the abundance of several species which are infre- 

 quent in the Midland and Mountain Zones, as well as by purely 

 Coastal species. In a sandy swamp two miles southeast of Towson, 

 Baltimore County, and therefore about seven miles from the "Fall- 

 Line" are to be found Liquidambar styracifiua,, Ilex opaca, Magnolia 

 virginiana, Cletlira alnifolia and Viburnum nudum, all of which, 

 excepting Ilex opaca, are unknown from any other stations off the 

 Coastal Plain. On the southern slope of Sugar Loaf Mountain, in 

 Frederick County, 32 miles from the "Fall-line," the soil is a coarse 

 sand derived from disintegration of the underlying sandstone. In 

 certain places where the topographic conditions render this soil con- 

 stantly wet or even saturated, may be found Chionanthus virginica, 

 Ilex verticillata, Eupatorium verbcnacfolium, Eupatorium rotundi- 

 folium, Bynchospora glomerata, Xyris caroliniana, Triaclcninn rir- 

 ginicum and Juncus dicliotomus, all of which are common in the wet 

 sandy habitats of the Coastal Zone, but are rare in the Midland Zone, 

 being found only in such habitats as that just described. In like 

 manner the species common in the Midland Zone may be found infre- 



