54 HARPER 



The manner of dissemination is not definitely known for about 

 half the species. Some 25 species have wind-borne seeds or 

 achenes, about half as many have stiff stems which scatter the 

 seeds short distances by waving in the wind, and some of the 

 shrubs have fleshy fruits. Few if any have fruits adapted for 

 attaching themselves to animals. 



The 98 species represent 70 genera and 33 families. The 

 largest family is Compositas, constituting a fifth of the whole list, 

 but the largest genus is Polygala, with seven species. The mono- 

 cotyledons constitute 22.3% of the total number of angiosperms. 



The ranges of these plants are more restricted than those of 

 dry pine-barrens. They are typical coastal plain plants, only 

 about 1 5 of them being known in other parts of the United States. 

 These 15 are divisible into three classes, namely, those which 

 belong more properly to the dry pine-barrens already discussed, 

 those which are widely distributed in the coastal plain and 

 glaciated region but rare elsewhere, and those which occur in 

 damp sandy places at a few isolated stations in the southern 

 mountains and Piedmont region. Those of the two latter classes 

 belong also to the next habitat group to be discussed. 



Within the coastal plain many of the intermediate pine-barren 

 plants do not extend farther inland than the Altamaha Grit region, 

 but nearly all of them grow also in the flat country toward the 

 coast, where similar habitats predominate. Many of them extend 

 well down into Florida, but none reach the tropics, with the 

 possible exception of Pinus Elliottii. Less than a third of the 

 number of species range as far north as Virginia, so as to be in- 

 cluded in the "Manual region. " 



4. Moist Pine-Barrens. 



The lower slopes of every little valley in the region under 

 consideration are perpetually moist. The explanation of this 

 is simple. The Columbia sand holds water like a sponge, and 

 the Lafayette clay a short distance beneath prevents it from 

 percolating deep into the earth. The sand being a poor con- 

 ductor of heat protects the water in it from evaporation, so 

 whatever water the soil contains is constantly trickling down 

 the slopes and seeping out at the lower levels. 



