FREE INSTITUTE OF SCIENCE 



VEGETATION OF SOUTH FLORIDA 



SEA STRAND FORMATIONS 



The sea beaches and the undulating surface back of them in South 

 Florida consist of two kinds of materials, as previously indicated. Silicious 

 sand is the material which forms the beaches and dunes of the coast north 

 of Key Biscayne, while Soldier Key and the islands south of it have their 

 sea beaches formed of calcareous sand, which represents the ground-up 

 particles of coral, shells and calcareous seaweeds. The hills formed by wind- 

 blown silicious sands may reach considerable elevation, while those of cal- 

 careous sand are usually low, because the particles, through the action of rain 

 water, are often cemented together and are not blown about by the fickle winds. 



Sea Beach Plant Formation. The observations which follow are based 

 on an examination of the beaches of silicious sand in South Florida. Little 

 or no study was made of the flora of the calcareous beaches of the keys, the 

 vegetation of which for the most part is excluded from this account. The 

 sand which forms the beaches is a medium fine quartz sand and rather angular. 

 Its color varies from gray, the prevailing tint, to pale yellow, to light reddish 

 brown. We may distinguish three subdivisions of the beach, viz., the lower, 

 or front, beach, the middle beach and the upper beach. The lower beach is 

 without visible vegetation, as it is covered and uncovered by the rising and 

 falling of the tides, and is exposed to the full force of the breakers, when the 

 surf is at all rough. It slopes gradually seaward with a gentle declination, 

 so that the bathing is usually safe. This is the submerged beach. The middle 

 beach is characterized by the material that has been cast ashore by the higher 

 tides. It is covered with a miscellaneous flotsam and jetsam, such as sea- 

 weeds, fruits, and seeds, driftwood, broken shells, animal remains, and the 

 like. The lower part of the middle beach is without rooted plants, but if it is 

 wide, we find its upper levels invaded by plants that are normally found as 

 tenants of the upper beach, which stretches to the foot of the dunes. The 

 middle beach and the upper beach sand is usually dry when the tide is out, 

 but the lower beach sand shows the presence of a considerable amount of in- 

 terstitial water which is demonstrated when the foot is pressed into sand 

 which whitens, owing to the expulsion of water, while as soon as the foot is 

 lifted the original gray color is restored. A study of the beach flora of sub- 

 tropic Florida naturally resolves itself into an examination of the flora of the 

 upper beach. Observations were made at five widely separated localities, 

 viz., the beaches of Anastasia Island off St. Augustine, Ormond Beach, Ocean 



