540 



SCIENCE 



[N. S. Vol. XXV. No. 640 



ber of endemic species, also that many species 

 which are not endemic grow more abundantly 

 or vigorously in such places than in other 

 parts of their ranges. 



A well-known example of a center of dis- 

 tribution is the southern Appalachian region, 

 which has the greatest variety of trees to be 

 found anywhere in temperate eastern North 

 America, most of which grow larger there than 

 anywhere else, and many species are now con- 

 fined to that region, though some of them were 

 doubtless more widely distributed in pre- 

 historic times. Isolated islands and moun- 

 tain peaks in all parts of the world are also 

 noted for their endemic species. 



Our Atlantic coastal plain (shown on map 

 which was>exhibited), though in some respects 

 a unit, contains several fairly well defined 

 centers of distribution. Beginning at the 

 northern end, the first center to be considered 

 is the so-called ' pine-barrens ' of New Jersey. 

 From the available literature if would seem 

 that the following species are either confined 

 to that region or else are much commoner in 

 New Jersey than in adjoining states. 



Schizcea pusilla, Sporololus compressus, Di- 

 chromena colorata, Bhynchospora pallida, B. 

 Enieshernii, B. Torreyana, Xyris fimbriata, 

 X. flexuosa {torta of most authors), Erio- 

 caulon Parkeri, Juncus Gcesariensis, Aiama 

 Americana, Eelonias hullata, Xerophyllum 

 asphodeloides, Oceanoros leimanthoides. To- 

 fieldia racemosa, Uvularia sessilifolia nitida, 

 Aletris aurea, Lophiola aurea, Oyrotheca iinc- 

 toria, Pogonia divaricata, Arenaria Oarolin- 

 iana, Drosera filiformis, Corema Con/radii, 

 Ilex glabra, Hypericum adpressum, Bhexia 

 aristosa, Dendrium huxifolium, Pyxidanthera 

 hariulata, Gentiana Porphyria, Sclerolepis 

 uniflora, Chrysopsis falcata. Coreopsis rosea. 



Most of these are monocotyledons, and there 

 are more species of MelanthaccES in the list 

 than of any other one family. 



The next well-marked coastal plain center 

 seems to be in the southern comer of North 

 Carolina. The following species are rarely 

 if ever seen more than 100 miles from 

 Wilmington. 



Tofieldia glabra, Hypoxis micrantha. 



Dionoea muscipula, Kalmia cuneata. Coreopsis 

 falcata, Leptopoda Curtisii. 



The following species of wider distribution 

 seem to be more abundant within about 50 

 miles of Wilmington than they are at a dis- 

 tance of 100 to 200 miles in either direction. 



Selaginella acanihonota, Pinus palustris, P. 

 serotina, Aristida stricta, Campulosus aroma- 

 ticus, Dichromena latifolia, Zygadenus glaber- 

 rimus, Lilium Catesboei, Smilax laurifolia, 

 Eabenaria hlephariglottis, Nymphma sagitti- 

 folia, Amorpha heriacea, Polygala lutea, P. 

 ramosa, Gordonia Lasianthus, Cyrilla racemi- 

 flora, Clethra alnifolia, Vacdnium crassi- 

 folium, Sabbatia lanceolata, Carphephorus 

 bellidifolius. Aster squarrosus, Marshallia 

 graminifolia. 



By far the greatest center of pine-barren 

 plants or perhaps an aggregation of two or 

 more sub-centers, is in Georgia and northern 

 Florida, Probably three fourths if not nine 

 tenths of all pine-barren species can be found 

 in Georgia, at least a dozen are confined to 

 that state, and many more to Georgia and 

 Florida together. In the Altamaha Grit 

 region (the middle third of the coastal plain) 

 of Georgia there are nearly 150 species on 

 sand-hills, about the same in dry pine-barrens, 

 200 in moist pine-barrens, and 75 in pine- 

 barren ponds. These numbers are undoubtedly 

 larger than for the same habitats in any other 

 state unless it is Florida. 



In subtropical Florida there are, of course, 

 many plants not found farther north, but 

 practically all of these center in the tropics, 

 and are therefore outside of the region under 

 consideration. 



Going westward from Florida we find in the 

 vicinity of Mobile and Pensacola a center 

 comparable with that in southern North Caro- 

 lina. To this belong Myrica inodora, Sar- 

 racenia Drummondii, Drosera filiformis 

 Tracyi, Pitcheria galactioides, and perhaps 

 Carphephorus Pseudo-Liatris. Chamwcpparit 

 thyoides and Sarracenia purpurea, which are 

 as common within fifty miles of Mobile Bay 

 as they are in New England, seem to be en- 

 tirely wanting at twice that distance, and do 

 not appear again within two or three hundred 

 miles, as far as known. 



