BLACK GUM SWAMP. 417 



FRESH WATER FORMATIONS. 

 HYGKOPHILE FOREST. 



By far the greater part of the Hygrophile Forest of the region is 

 embraced within the limits of the Great Dismal Swamp proper. That 

 extensive morass has already been described, as to its physical char- 

 acteristics, in the subdivision on geography and physiography, and 

 the description need not be repeated in this place. As was there 

 mentioned, certain smaller outlying tracts of swampy forest border 

 the sluggish rivers which for the most part arise in the Great Dismal 

 itself. There are also similar areas, of various size, scattered through 

 parts of the region still more remote from the principal swamp, note- 

 worthy being a considerable portion of "The Desert" at Cape Henry. 

 The vegetation of these outlying swamps is very similar to that of 

 the Great Dismal, and does not require to be separately treated. 



Two principal formations are to be distinguished in the Hygrophile 

 Forest: (1) The Black Gum or Dark swamp, covered with heavy 

 deciduous forest; and (2) the Light, Open, or Juniper swamp, origi- 

 nally in great part covered with an evergreen forest of white cedar 

 or "juniper" (C hamaecyparis thy aides), but now, in many places 

 almost destitute of trees and bearing a growth of shrubs, of cane 

 (Arundinaria macrosperma) , and of ferns and peat moss. The first 

 is in great part a virgin formation; the second, while composed entirely 

 of indigenous species, owes its present condition largely to the work 

 of man. Other associations, belonging to the fresh-water marsh and 

 the aquatic formations, are subordinate elements in the plant cover- 

 ing of the swamps. They will be described under the formations to 

 which they ecologically belong. 



BLACK GUM SWAMP. 



This, the local name of the heavy deciduous forest, indicates the 

 predominance of the black gum (Nyssa biflora). (Plate LXVII.) 

 The formation is also known in the region as "Dark swamp." Its 

 larger trees are such as lose their foliage in the autumn, even the 

 prevailing conifer, the bald cypress (Taxodium distichum), being 

 deciduous. The only evergreen specie's among the large trees is 

 the short-leaf pine {Pinun toe da), and that is comparatively scarce 

 and unimportant. Such deciduous forest, alone occupies the low, fiat 

 banks of the rivers above mentioned, and it is likewise characteristic- 

 ally developed within the Great Dismal Swamp proper, especially in 

 the central portion about Lake Drummond. Fine tracts of it extend 

 for 10 kilometers or more northwest of the lake, and cover large 

 areas near the eastern periphery of the swamp. Indeed, areas occu- 

 pied by this type of vegetation intervene between tracts of "Light 

 swamp" in almost every part of the Great Dismal. 



This is generally the wettest of the palustrine forest, ami in no 



