8 TRANSACTIONS OF WAGNER 
9 VEGETATION OF SOUTH FLORIDA 
stead, it reaches a height of 2 to 3 m. and on the keys of Florida, as on Big 
Pine Key, it becomes a good-sized tree. This variation in size is attributed to 
the influence of the low night temperature in winter and the occasional frost. 
That these factors, which influence the height of the silver palm, and its 
northern range, are also active as limiting factors in the distribution of many 
tropic species is probably true, but in the absence of experimental data, it is 
perhaps better to advance this view of climatic influence as a provisional 
hypothesis. 
LONG-LEAF PINE (PINUS PALUSTRIS MILL.) FORMATION 
This formation south of the 27° 30’ north latitude is a continuation, or 
southern lobe, of an extensive region called in Harper’s report on peat the 
South Florida Flatwoods; and in the Tenth Census Report on Cotton Produc- 
tion by Dr. Eugene A. Smith (VI: 200 (1880) with map opposite page 187) 
the Long-leaf Pine Region. This region consists of rolling pineland and pine 
flats, or flatwoods. The rolling pinelands occupy rolling, or gently undulating 
country sufficiently elevated to secure good drainage. The whole area thus 
included is about 15,120 square miles. The pine flats, or flatwoods region, 
follows the direction of the coast margining the rólling pineland by a strip of 
country of greater, or less width, where the land is low, flat, or badly drained. 
This region embraces an area about 11,250 square miles in extent. Beside 
this belt, there is a tract of elevated, flat, wet land on the divide between the 
Atlantic Ocean and the Gulf of Mexico, which comprises another 2,280 square 
miles, making for the flatwoods region a total of 13,530 square miles, so that 
altogether the long-leaf pine, Pinus palustris Mill., covers 15,120+13,530= 
28,650 square miles of country. 
As far as this vast region of pineland concerns this monograph, it is 
comprised in the counties of Polk, Manatee, DeSoto and Lee. The more or 
less sandy soil of the flatwoods is usually underlaid by a clay substratum, or a 
densely packed sand, which is impervious, and this together with the flat sur- 
face prevents proper drainage, so that swamps are associated with flatwoods. 
Throughout the long-leaf pine region, pine barrens occupy the poorer classes 
of soil. The growth upon these is mostly long-leaf pine, black-jack oak, 
scrubby oaks of other species. In the flat pine barrens saw-palmetto and 
gallberry bushes are common. “While the undergrowth of shrubs in the 
