GEOGRAPHY OF CENTRAL FLORIDA 213

mainly confined to the lake region, and are sometimes called bayheads. About half the trees in them are evergreen, and fire is rare. They are little utilized at present, but will probably be. drawn upon for some kinds of timber when the country is more thickly settled.
 Calcareous swamps. Swamps whose water is somewhat calcareous on account of coming from limestone springs or standing for awhile in contact with limestone or marl differ from the sour or non-alluvial swamps just described in having more deciduous and usually larger trees, particularly cypress (Taxodium dis'tich mu). They have been described in the Third Annual Report, pp. 271, 279-281, and Seventh, pp. 176-178. They are most common in the Gulf hammock and lime-sink regions, and in fact are almost the only kind of swamps in those regions. They also occur in the lake region, around some of the larger lakes and along the Wekiva River and its tributaries. They grade into the low hammocks to be described next, the only fundamental difference apparently being the amount of water present. In the lake region they often pass abruptly into saw-grass marshes, on which they may be gradually encroaching. Fire seems to be a negligible factor.
 The cypress is valuable for timber, but the other trees are comparatively unimportant.
 Lowhammocks (fig. 25). Dense shady forests with soil perpetually moist, but not quite wet enough to be called swamps, are called low hammocks. Those in central Florida all seem to be more or less calcareous, and they are especially characteristic of the Gulf hammock region, but are quite common in the lke region and east coast strip, and occur in most of the others. They have been described in the 7th Annual Report, pp. 175-176. On the upland side they often pass into semi-calcareous high hammocks describeda farther on), or even into sandy hammocks. Fire is very rare, as in all other hammocks.
 Sofne of the trees are valuable for timber, and the soil is generally quite fertile, perhaps partly on account of washings from the neighboring uplands; and where it can be easily drained it is often cultivated in vegetables. Much if not most of the truck farming in Seminole and Sumter Counties is in places forme.rly occupied by this type of vegetation, and one of the largest orange groves in the latter is in what seems to have been a low hammock, through probably drier than the average.