108 HARPER 



number of species was so small that the results which would 

 have been obtained by the usual method might have been 

 misleading. 



Some of the interesting facts brought out by the above table 

 are as follows. Dry pine-barrens cover the greatest area and 

 moist pine-barrens have the richest flora. Moist pine-barrens 

 have the smallest proportion of trees and shrubs and consequently 

 the largest proportion of herbs. The swamps of rivers of the 

 second class have the smallest proportion of herbs and by far the 

 largest proportion of trees. The largest proportion of shrubs 

 is found in sand-hammocks, with non-alluvial swamps second. 

 Sand-hill ponds have the largest percentage of monocotyledons, 

 with moist pine-barrens next, and the three last groups the 

 smallest. Cypress ponds, shallower pine-barren ponds, and sand- 

 hill ponds seem to have the longest flowering periods, and river- 

 swamps, hammocks, and bluffs the shortest. 



In general the smallest percentages of monocotyledons and the 

 shortest flowering periods belong to those groups a large propor- 

 tion of whose members range inland to the Piedmont region and 

 mountains, while the typical coastal-plain habitats have many 

 monocotyledons and longer flowering periods. Investigations 

 of this kind will perhaps hereafter throw a great deal of light 

 on the origin and age of the flora of various other parts of Eastern 

 North America. 



It will be noticed that the percentages in the second column add 

 up 168.2. This gives an idea of the extent of overlapping of 

 the different habitat -groups. If the number of species common 

 to two or more habitats decreases in geometrical progression with 

 the number of habitats, which is not an unreasonable supposition, 

 then about 60% of the species would be confined to one 

 habitat each, 24% to two, 10% to three, 4% to four, and so on. 



Relations of the Typical Habitat-Groups to Each 



Other. 



Having completed a preliminary outline of the habitat -groups 



which may be considered fairly typical of the Altamaha Grit 



region, in which outline they have been treated in linear sequence, 



it will be appropriate to pause at this point and show their re- 



