8 HARPER 



of vegetation based on these factors is in many respects ideal. 

 While the same or similar types of soil and topography sometimes 

 occur in connection with different geological formations, yet in 

 that case they are often separated by such distances or barriers 

 that plants cannot readily migrate from one formation to the 

 other, and the floras associated with them are then perceptibly 

 different. 



In Georgia, and especially in the coastal plain, where most of 

 the writer's field work has been carried on, similar types of 

 topography and vegetation seem almost invariably to indicate 

 similar geological conditions; and for an area of that size and 

 character a phytogeographical classification based on geology 

 seems to be the only logical one. This may not be equally true 

 everywhere else, but the same principles have been recognized 

 by Hollick on Staten Island and elsewhere in that neigh- 

 borhood, Gattinger in Tennessee, Smith in Alabama and Florida, 

 and Hilgard in Mississippi, and given prominence in their writings. 

 Several other botanists and geologists have noted the intimate 

 relations between botany and geology in a superficial way, but 

 there have been comparatively few attempts in this country 

 as yet to generalize observations of this kind or to explain them. 1 



1 The following easily overlooked references to this subject, most of 

 them written before "ecology" became popular, and not exhaustive 

 enough to be mentioned in the bibliography at the end of this paper, 

 may be of interest : 



Porcher, F. P. Resources of the Southern Fields and Forests, xi. 1869. 

 Flagg, Wilson. Woodsand Byways of New England, pp. 4, 5, 31, 32. 1872. 

 Hollick, Arthur. Relations between geological formations and the 



distribution of plants [on Staten Island, N.Y.]. Bull. Torrey Club 7 : 14. 



15. Feb., 1880. 

 Britton. N. L. On the existence of a peculiar flora on the Kittatinny 



Mountains of northern New Jersey. Bull. Torrey Club 11: 126-128. 



1884. 

 Britton, N. L. Note on the flora of the Kittatinny Mountains. Bull. 



Torrey Club, 14:187-189. 1887. 

 Raymond, R. W. Indicative plants. Trans. Am. Inst. Mining Engineers, 



15:644-660. /. 1-3. 1887. Abstract in Bull. Torrey Club 14: 127. 1887. 

 Evans, H. A. The relation of the flora to the geological formations 



in Lincoln County, Kentucky. Bot. Gaz. 14: 310-314. 1889. 

 Coville, F. V. The effect of soil on the distribution of plants. Rep. 



Geol. Surv. Ark., 1888 4 : 246-247. 1891 



