244 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



Atlantic coast, probably because the prevailing winds do not blow 

 toward the land. Few of the moving dunes are more than ten feet 

 high ; but some of the ancient dunes on the mainland and St. James 

 Island are 40 or 50 feet above sea-level. Among these high old 

 dunes are some approximately circular depressions apparently identi- 

 cal in form with some in Middle and peninsular Florida which are 

 supposed to have been formed by the solution of underlying lime- 

 stone; but here there is no limestone anywhere near the surface, and 

 wind seems to be the only agent which could have formed the hol- 

 lows, though the details of the process are not fully understood. 



Ponds, springs and streams are scarce, on account of the nar- 

 rowness of the coast strip and the porosity of the sand ; but in some 

 of the dune hollows, as in similar hollows in the flatwoods close by, 

 there are tyty bays (described in the 3d Annual Report, p. 265). 



Vegetation Types — Some of these have been briefly indicated 

 above in the discussions of geology and topography. Typical salt 

 marshes, such as are common on the Atlantic coast, are scarce and 

 small in West Florida, but there is a good deal of brackish marsh 

 around the mouths of rivers and creeks. The marshes are treeless, 

 and the moving dunes likewise. The stationary dunes nearest the 

 coast have a sparse growth of slash pine and a few other trees, and 

 evergreen shrubs. A little farther back there is a good deal of spruce 

 pine (Piniis claiisa), which thrives in the poorest sand, while on the 

 highest old dunes on the mainland, where the leaching is counter- 

 acted to some extent by the soil fauna, long-leaf pine and blackjack 

 oak prevail. Among or near the old dunes are areas of flat pine land 

 with tyty bays, which may belong to the flatwoods region, but they 

 are so intimately mixed with the dunes that it was difficult to sep- 

 arate *"hem in making up the plant lists. 



Fire is a negligible factor in the coast region, partly because the 

 islands and peninsulas are well protected by water, and partly be- 

 cause most of the vegetation is too sparse to carry fire. In some hol- 

 lows and on slopes near waterways, where there is sufficient protec- 

 tion from wind and sun for humus to accumulate, there is hammock 

 vegetation. 



Plants — The following list is based on observations made on 

 12 different days, distributed through the year as follows: April, 

 I ; May, 2; June, 4; July, i ; August, I ; September, i ; December. 2. 

 It cannot be very complete, though, for my opportunities for visit- 

 ing the outer islands have been very limited. And it probably in- 



