290 FLORIDA GEOLOGICAL SURVEY THIRD ANNUAL REPORT.
TREES
Pinus serotina (black pine) Gordonia Lasianthus (bay)
Magnolia glauca (bay) Persea pubescens (red bay)
SHRUBS
Aralia spinosa (prickly ash) (most- Smilax laurifolia (bamboo vine)
ly near the edge)
HERBS
Osmunda cinnamomnea (a fern)
The width of this part of the swamp is about 200oo yards, and at that distance from the edge the peat is about 8 feet deep. At the time of my visit, in January, 1909, the swamp seemed to have been burned over within a year or two, which had lowered the surface of the peat a few inches, and also allowed blackberry briers and a few other weeds to come in. Some parts of it had also been ditched and cultivated to some extent. Analyses of peat from this locality (No. 8.2) show it to contain only about half as much ash and sulphur as that from nearer the river, and its fuel value is higher.
THE "INFUSORIAL EARTH" BOG.
About 3 miles east of Tavares, on the north side of Lake Dora, is a bog covering nearly Ioo acres, of the peat prairie type already described, which on the surface looks like many other small filled lakes in the same region. But it differs from all others that I have seen in the composition of the ash of the upper layers of the peat. A chunk from near the surface contains so much mineral latterr that when dry it has a grayish color, instead of the usual black or dark brown. This mineral matter has been found to consist mostly of the shell of diatoms, and when such peat is burned the diatoms remain as a very fine and light white powder, having much the appearance of flour. (The uses of this material will be mentioned in a subsequent chapter.) A ditch about six feet deep, leading through a low ridge of scrub to the eastward, has altered conditions to the extent of keeping the average water-level a foot or so below the surface of the peat, when it was originally no doubt a little above the surface.
According to Hon. H. W. Bishop of Eustis, who was formerly interested in this property, the ditch was dug about 1896 by a man who intended to raise tobacco on the drained peat. In this he was