Vol. 6 No. 12 



TORREYA 



December, 1906 



LIBRARY 



SOME HITHERTO UNDESCRIBED OUTCROPS OF new YORK 

 ALTAMAHA GRIT AND THEIR VEGETATION botanical 



GARDEN 



By Roland M. Harper 



In my phytogeographical sketch of the Altamaha Grit region 

 of Georgia,* as well as in some earlier papers more accessible to 

 botanists,t I have called attention to the very limited occurrence 

 in the Georgia pine-barrens of outcrops of a kind of rock which 

 is not exactly matched in any adjoining state. These rocks have 

 comparatively little interest for the geologist, being merely a 

 locally indurated phase of a formation of mottled clays and 

 cross-bedded sands which occurs just beneath the superficial 

 Lafayette loam and seems to cover the greater part of the coastal 

 plain from South Carolina to Florida and Mississippi, if not 

 farther ; but to the phytogeographer they are extremely signifi- 

 cant. 



The vegetative covering of any of these rock outcrops can 

 usually be divided into three classes : first, species more common 

 in other habitats in the pine-barren region, which have gained a 

 foothold on the rocks and manage to survive amid uncongenial 

 surroundings because competition is not very severe there ; 

 second, species which are common on flat granite or sandstone 

 rocks in the upper districts but are not known elsewhere in the 

 coastal plain ; third, a few species not known outside of the Al- 

 tamaha Grit region of Georgia, which are nearly if not quite 

 confined to these particular rocks. 



1^^ *Ann. N. Y. Acad. Sci. 17: 22, 41-44. pi. i. 1906. 



CD f Torreya 4 : 139, 140. 1904; Fern Bull. 13: 3, 15. 1905. Bull. Torrey 



*— Club 32 : 143-145, 152, 166, 168, 170. 1905. 



I [No. II, Vol. 6, of Torreya, comprising pages 217-240, was issued November 



t"^ 26, 1906.] 



S 241 



