16 HARPER 



Magnolia graudiflora, and Sebastiana ligustrina. 1 And in almost 

 any river-swamp in the Eocene region we can find Taxodium 

 distichtim, Sabal glabra, Planera aquatica, and Brunnichia cirrhosa, 

 whose ranges (in Georgia at least) terminate abruptly at the fall- 

 line. Furthermore, on almost every square mile of South Georgia 

 are sandy bogs containing still other species which rarely or never 

 cross the fall-line. 



4. Lower Oligocene. Next to the Eocene region, and appar- 

 ently without any sharp demarcation between them, is the area 

 of the Lower Oligocene formations (Jacksonian, Vicksburgian, 

 etc.). Including the Jacksonian (which by many geologists is 

 placed in the Eocene, but from a phytogeographical standpoint 

 seems more closely allied with the Vicksburgian), this division 

 covers about 19% of the area of South Georgia. 



The Lower Oligocene rocks are partly soft limestone and partly 

 siliceous. In that part known as the lime-sink region (which 

 is mostly near the Flint River), caves, subterranean streams, 

 large ponds and smaller basin-like depressions are common. 

 Surface streams are rare ; one can often travel miles without seeing 

 running water. The topography is comparatively level, with 

 rarely anything that can be called a hill. Practically the whole 

 region, except on steep banks of streams, is covered with the 

 Lafayette and Columbia formations, but the influence of the 

 limestone beneath is sometimes noticeable in the vegetation. 



In this region the pine-barrens (i. e., the forests in which Pinus 

 palustris is more abundant than all other arborescent species 

 combined, and the trees do not grow thickly enough to sensibly 

 diminish the quantity of light which reaches the ground) begin, 

 and from there to the coast they cover about nine-tenths of the 

 country. The pine-barrens do not begin suddenly, however. 

 At their inland limit the pines are mixed with a considerable 

 quantity of oaks, mostly of two species with broad leaves rusty 

 beneath (Q. Marylandica and Q. digitata). Toward the coast 

 the quantity of oaks becomes less, and the two species just men- 

 tioned are gradually replaced by others with narrower or paler 

 or more glossy leaves (Q. brevifolia, Q. Margaretta, Q. Catesbai). 



1 See also Bull. Torrey Club 31: 15-16. 1904; 32: 453. 1905. 



