292 FLORIDA GEOLOGICAL SURVEY-THIRD ANNUAL REPORT.
WATER-HYACINTH PEAT.
The water hyacinth, Piaropus (formerly Eichhornia, once Pontederia) crassipes, a beautiful ornamental aquatic plant,
native of South America, began to escape from cultivation and make itself a nuisance in Florida about twenty years ago. It thrives in our lakes and estuaries probably almost as well as in its native haunts, and for a time it threatened to close the St. Johns River to navigation.* For some reason not altogether obvious, it iF mtuch less troublesome now than formerly. having apparently reached a state of Zquilibrium. It has some redeeming features, too. It is undeniably a beautiful plant when in bloom, cows like to eat it, and finally, it may be an important source of peat.
For it grows pretty rapidly, and in just the places which are best adapted for the formation of peat. It is never found in salt or swift water, in ponds which dry up completely, or in streams subject to great fluctuations; and not often in muddy or calcareous water. Its favorite habitat is permanent ponds, lakes and estuaries. sometimes floating on the water, and sometimes taking root on mucky or peaty shores, but in either case constantly decaying and producing peat.
The Withlacoochee River near Istachatta, at the northeastern corner of Hernando County, (and doubtless elsewhere) was in January, 1909, completely covered from shore to shore with a dense mass of water hyacinth, and I was told that a man could take a couple of planks of sufficient size and with their aid walk across the river on the plants. In the edge of the river I noticed some logs partly submerged, which could not have been there many" years, and on top of them a few inches of peat, evidently formed mostly from the hyacinths. Associated with the water hyacinth in this river, and partly supported by it, I noticed Decodon verticillatus, a weak herb-like shrub, and the following aquatic herbs.
*An interesting account of its status in Florida, written by Dr. H. J. Webber about the time it was at its worst, can be found in Bulletin I8 of the Division of Botany, U. S. Department of Agriculture, published in 1897.
At various times in the last ten years the U. S. Army engineers have conducted experiments in Florida, mostly on the St. Johns River, with a view to exterminating the water hyacinth, sometimes by mechanical and sometimes by chemical means. (See Reports of the Chief of Engineers, 1899: 276-277, 1612-1613; 190: 315, 1985; 1901: 1746-1749; 1903: 184-1186; 1904: 1712-1713; 190O5 1318; 1906: 330-331, 1234-1239; especially the last.) Spraying with poisonous liquids was found to be most effective, but had the serious drawback of poisoning cattle which fed on the plants.