GEOGRAPHY OF CENTRAL FLORIDA 205

and therefore to be classed as thickets. The shrubs are nearly all evergreen, and the soil very poor and seldom cultivated.

 SMALL TREES
 Mangrove szcanps (fig. 37). On the margins of shallow quiet bodies of salt water from Bre.vard and Pinellas Counties southward are swamps composed of salt-loving small trees and large shrubs mainly tropical in distribution, particularly the black, red and white mangroves (Aviccnnia, Rhiophora and Laguncularia) and buttonwood (Conocarpus). The first-named extends northward in shrubby form to Cedar Keys and New Smyrna and perhaps farther. In extreme southern Florida the first two become trees of considerable size, and the red mangrove is used for tan-bark and the buttonwood for fuel.

















 Fig. 37. Mangrove swamp on inner side of Long Key, Pinellas County. The larger trunks at .the left belong to the black mangrove (Avicennia), and the innumerable erect pipe-stem-like objects are its aerating organs. The seedlings and smaller crooked trunks are red mangrove (Rhizophora): March ii, 1915.
 Tropical hammocks (fig. 34). The plants growing on shelI mounds along the Indian River in southern Brevard County are nearly all of tropical species, quite different from the species of more northerly distribution on sandy soils nearby,. The forests a.re very dense, and the trees rather small and crooked, though they all grow larger in the hammocks south of Miami, and in the