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103 



VEGETATION OF SOUTH FLORIDA 



or groups of species, is conditioned solely by amount of space, light and edaphic 

 influences. A very slight difference in the soil, drainage, depth below the 

 general surface of the pineland, amount of soil, quantity of standing water 

 and amount of light which penetrates between the pine trees makes a striking 

 difference in the composition of the vegetation of these banana holes. That 

 such slight differences of environmental conditions influence the character of 

 the vegetation is demonstrated by that of the snow patches found in the Euro- 

 pean Alps. These snow patches are, according to C. Schroter,* gently in- 

 clined flat, or concave spots that occur in the Alps and are saturated with 

 water from melted snow. If they exist as depressions filled with snow for a 

 long time, then there is deposited thick, black humus which owes its origin 

 to the snow. For this carries down from the air a quantity of organic dust, 

 wind-blown particles gather here, and the snow is thus made a catch-all 

 for such extraneous bodies. This habitat is characterized by lowness of 

 temperature, abundance of humus and permanent saturation of the soil. The 

 community of plants settling upon it in Switzerland is extremely constant. 



Similarly the limestone sinks in South Florida receive a large amount 

 of material washed into them from the surrounding pineland. These 

 materials consist of sand, and minerals leached out of the exposed surface 

 oolite, while in addition leaf mould, small branches, pine cones, etc., are 

 swept into the pot-holes and collect like the material does in the vortex of 

 water which rushes from a paved street of a city down into a grated culvert 

 provided to catch the surface run-off. Then too the herbaceous vegetation 

 of such sinks is protected in the bottom from sharp winds which visit South 

 Florida, and from the too direct rays of sunlight. Such concave spots are 

 usually moister, so that filmy fernsf (Hymenophyllaceae) are found growing 

 along their edges, while epiphytic orchids, ferns and bromeliads live attached 

 to the trees above. Many shade-loving plants find a suitable habitat here, for 

 the sunlight, first cut off by the surrounding pine trees, must pass the tree and 

 shrubby growth which fills the banana holes and receive an amount of light 

 conditioned by the depth of the well below the general surface of the pineland. 



Origin of Banana Holes and Hammocks. As the banana holes exist in all 



sizes from those which can be jumped across to those covering one hectare, a 



sharp distinction cannot be drawn between the vegetation of the larger banana 



holes and the smaller hammocks which occur in the same region. For example 



* Warming, Eug.: Ecology of Plants: 310.. fOn the authority of Ernst Bessey. 



