95 



Rock Hill is one of a group of several peculiar isolated hills 

 in the northern part of Washington County, Florida.* I would 

 estimate its dimensions roughly as about one-fourth mile long 

 (approximately north and south), one-eighth mile wide, and 50 

 feet high. Like the country for several miles in all directions, 

 it is covered with open forests of long-leaf pine, now^ badly 

 damaged by lumbermen, so that the rocks on it can be seen from 

 a considerable distance. On its slopes there are several hori- 

 zontal ledges of a pine-bark-colored rock which seems to differ 

 from the typical Altamaha Grit of Georgiaf only in being a little 

 more sandy, and this difference is apparent only on close inspec- 

 tion. Like the corresponding rock in Georgia, too, it never 

 appears on the summit of a hill, but always on slopes. (See 

 illustration.) 



It seems to be generally true that the flora of any particular 

 habitat is richest near the center of distribution of that habitat. J 

 This principle is illustrated by the vegetation of Rock Hill, 

 which is about 100 miles from any other known outcrop of the 

 same kind of rock. On the bare rocks, and on the thin soil 

 which covers them on gentle slopes, I identified the following 

 species (which are here arranged approximately in order of 

 abundance) : 



Pinus palustris 



Gaylussacia dumosa 

 Vaccinium nitidum 

 Chrysobalanus oblongifolius 

 Symplocos tinctoria 



Aristida striata 

 Chondrophora virgata 

 Chrotonopsis spinosa? 

 Panicum dichotomumPll 



Trees 



Shrubs 



Herbs 



Quercus geminata 



Batodendron arboreum 

 Callicarpa americana 

 Serenoa serrulata 



Pteris aquilina 

 Aster sp.§ 

 Laciniaria gracilis 

 Campulosus aromaticus 



* See Tenth Census U.S. 6: 224. 1884. 



tSee Bull. Torrey.Club 32: 134-144. 1905; Ann. N. Y. Acad. Sci. 17: 22-23. 

 1906. 



JSee Bull. Torrey Club 32: 149 (second paragraph). 1905; Ann. N. Y. Acad. 

 Sci. 17: 55, 78, 89. 1906; Torreya 7: 43. 44- i907- 



§One of the dichotomous panicums, at any rate. In July, 1906, I saw what is 

 probably the same thing on an outcrop of the same kind of rock in Washington 

 County, Georgia. 



il With rather large blue heads and narrow leaves. 



