42 



" Centers of Distribution of Coastal Plain Plants," by Roland 

 M. Harper. 



One of the most familiar phenomena of plant distribution is 

 that neighboring areas of equal extent often differ considerably 

 in the number of species they contain. And it usually happens 

 that a region with a rich flora (if a large enough area be taken 

 into consideration) contains a considerable number of endemic 

 species, also that many species which are not endemic grow more 

 abundantly or vigorously in such places than in other parts ot 

 their ranges. 



A well-known example of a center of distribution 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 confined to that region, though some of them 

 were doubtless more widely distributed in prehistoric times. 

 Isolated islands and mountain 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 pretty well de- 

 fined 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 it would seem that 

 the following species are either confined to that region or else are 

 much commoner in New Jersey than in adjoining states : 



Schi-zaca piisilla, Sporobolus conipresstis, Dic]iro))iena colorata, 

 Ryiichospora pallida^ R. Knieskernii, R. Torrcyana, Xyris fivi- 

 briata, X. flcxiiosa {torta of most authors), Eriocaulon Parkeri, 

 Juncus caesaricnsis, Abaina americana, Helonias btillata, Xero- 

 phylliim asphodeloides, Oceanoros leiinanthoides, Tofiddia race- 

 inosa, Uviilaria scssllifolia nitida, Aletris aiirea, Lophiola aiirea, 

 Gyrotheca tinctoria, Pogonia divaricata, Arenaria carolinia7ia, 

 Droscra jilifonnis, Corcma Conradii, Ilex glabra, Hypericum ad- 

 pressmn, Rhexia aristosa, Dendrmvi buxifolium, Pyxidanthera bar- 

 bulata, Gentiana Porphyria, Sclerolcpis tinifiora, Chrysopsis falcata, 

 Coreopsis rosea. 



Most of these are monocotyledons, and there are more species 

 of Melanthaceae in the list than of any other one family. 



