FREE INSTITUTE OF SCIENCE 
VEGETATION OF SOUTH FLORIDA 
79 
into the Caloosahatchee River at Ft. Myers, has the usual round-topped 
“Character. The dominant mangrove tree is Rhizophora mangle L. with its 
opposite, leathery leaves of a dark-green color and its pendent, plummet-like 
embryos hanging out of the ripe fruit. Associated with the mangrove and 
growing out of the muddy ooze of the stream bank are the buttonwood, 
Conocarpus erecta L., three species of shrubby Baccharis, viz., B. angustifolia 
Michx., B. glomeruliflora Pers., and B. halimifolia L., with such herbaceous 
plants as a grass, Distichlis spicata (L.) Greene, two sedges, Cyperus ferax Vahl, 
Fimbristylis Harperi Britton, Lythrum lineare L., Rhabdadenia biflora (Jacq.) 
Muell. Arg, Phyla nodiflora (L.) Greene, Monniera monniera (L.) Britton, Aster 
carolinianus Walt., Pluchea purpurascens (Sw.) DC., and the yellow com- 
positous shrub, Borrichia frutescens (L.) DC. (in flower and fruit). A gray 
lichen, Parmelia latissima Fee, is found attached to the trunks of the mangrove 
trees, as also an undetermined species of Arthothelium and a Physcia, perhaps 
P. stellaris. The large fern, Acrostichum aureum L., is an element of the 
mangrove thicket along Billy Creek, and the water-hyacinth, Piaropus crassipes 
(Mart.) Britton, drifts in between the arched roots of the trees that line the 
shore. As this plant is so abundant in the rivers and lakes of Florida, it is 
suggested that it might be gathered and spread on the sandy fields of the state 
as a fertilizer, supplying by its decay a certain amount of humus to such soils. 
Instrumental Study of the Mangrove Formation.—The better to judge of 
the exact conditions which control in the mangrove thickets several instru- 
ments of precision were carried to South Florida on the last two trips. An 
hydrometer, reading to four decimal places, was used to determine the salinity 
of the water, a soil thermometer to get the temperature of the mud about the 
roots of the trees, an air thermometer to secure the temperature of the air and 
an hygrometer to test the humidity of the air. The hydrometer readings are 
most instructive, and the other data while very incomplete serve as an index 
of conditions that may prevail in the thicket at noon on a bright sunny day. 
The hydrometer readings are given below: 
Sp. gr. Temp. 
Océan water, surf at Palrylabd. reae reete л 1.0240 30° 
Bay Biscayne water, Mangrove Area 1.0235 30° 
Water at mouth of Miami River .0999 a 
Mangrove border, Miami River. .0999 ай" 
ТАЛАУ up; Ма КӨ C vr И .0999 27° 
Water at fork of Miami Уер dover sexe ee .0999 27° 
Water at outlet of Everglades.................. .0998 28° 
Everglade water in Miami Branch Canal......... .0997 a1" 
3 
