PEEFACE. 



This Flora contains descriptions of the seed-plants known to the author 

 to grow naturally on the islands of the Florida Reef from Virginia Key to 

 Dry Tortugas. These islands are known collectively as the Florida Keys, 

 and they lie in the form of a parabola with a length of about two hundred 

 and twenty-five miles. There are approximately two hundred named 

 islands. They are divided naturally into four groups which are described 

 below. 



At the northeastern end of the chain are two sand islands, namely 

 Virginia Key and Key Biscayne. These may be designated the Upper 

 Sand keys ("U. S. keys"). 1 These two bodies of sand are really mere 

 detached portions of the slender coastal peninsula of sand-dunes extending 

 along the eastern side of peninsular Florida. 



Seven miles south of Key Biscayne a second group of islands appears. 

 These are composed of coral-rock, and extend from Soldier Key, for a 

 distance of about one hundred and twenty miles, to the West Summerland 

 or Spanish Harbor Keys. The islands are for the most part greatly 

 elongated and with the long axis in a curve following the general trend of 

 the adjacent mainland. This group is known as the Upper keys (" U. 

 keys"). 



The third natural group of islands begins with No Name Key and 

 Little Pine Key and extends in a westerly direction for a distance of about 

 thirty miles, to Key West. The islands of this group are composed of 

 Miami Limestone, and although irregular in shape, the long axis is nearly 

 north and south, thus also differing from those of the previous group. 

 They are known collectively as the Lower keys (" L. keys "). 



The fourth group of islands lies to the westward of Key West and 

 reaches well into the Gulf of Mexico. They are composed of sand, and 

 may be designated the Lower Sand keys ("L. S. keys"). 



The Upper Sand keys maintain, for the most part, a sand-dune and 

 hammock flora which is related to that of the coastal peninsula to the 

 north. The Upper keys are naturally clothed with a dense hammock growth 

 of tropical hardwood shrubs and trees, and palms; they closely resemble 

 many of the Bahama islands. The Lower keys are more varied in their vege- 

 tation, supporting large areas of pineland and palmland, as well as exten- 

 sive hammocks. Their vegetation indicates close relationship to Cuba, 



1 This abbreviation and the abbreviations of the subsequently mentioned 

 groups are used on the following pages to indicate the geographical distribu- 

 tion of the species of plants growing in the region under consideration. 



