326 HARPER 



Many interesting conclusions can be drawn from this table, 

 but only a few of them will be mentioned here. It will be noticed 

 first of all perhaps that Cyperaceae occur in all the habitats, 

 Compositae in all but one, Ericaceae in all but three, Grami- 

 neae in all but four, Scrophnlariaceae in all but five, and Orchi- 

 daceae in only six. It happens that intermediate pine-barrens 

 is the only habitat in which all these families are repre- 

 sented. 



If we add together the figures in each row and divide by the 

 number of species in the corresponding family, we shall get a 

 ratio representing roughly the adaptability to different habitats 

 of the species in each family. In this respect Ericaceae lead, 

 with a ratio of 2.87, and Gramineae come last, with 1.22. 

 This is perhaps correlated with the fact that Gramineae are more 

 characteristic of old regions and Ericaceae of new regions, in 

 temperate Eastern North America at least. The ratio for the 

 whole Altamaha Grit region was shown on page 108 to be about 

 1.68. 



It will be noticed further that Orchidaceae do not usually 

 associate with Cupuliferae, Leguminosae, or Euphorbiaceae, and 

 that the habitats in which the three last-mentioned families 

 do not occur contain nearly twice as many monocotyledons (see 

 page 107) as those in which they do. This may indicate that 

 these three families are comparatively highly specialized with 

 respect to the orders to which they belong. 



To eliminate from the above table differences due to the 

 greater number of species in some habitats than in others, we 

 should express the figures in each column in terms of their 

 ratios to the number at the bottom of the column. Doing this, 

 we would find that while Compositae are most numerous in dry 

 pine-barrens, they are most prominent in intermediate pine- 

 barrens where they constitute 21% of the flora. Likewise 

 Leguminosae constitute about 17% of the flora of dry pine- 

 barrens and sand-hills. Cyperaceae are much more numerous in 

 moist pine-barrens than anywhere else, but most prominent in 

 cypress and escarpment ponds. Gramineae, too, have nearly 

 twice as many representatives in moist pine-barrens as in any 

 other one habitat, but are more prominent in the shallow pine- 



