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VEGETATION OF SOUTH FLORIDA 



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 ah 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. 



Ocean water, surf at Fairyland 1.0240 30 



Bay Biscayne water, Mangrove Area 1.0235 30 



Water at mouth of Miami River 0999 27 



Mangrove border, Miami River 0999 27 



Halfway up, Miami River 0999 27 



Water at fork of Miami River 0999 27 



Water at outlet of Everglades 0998 28 



Everglade water in Miami Branch Canal 0997 31 



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