312 



THE PLANT COVERING OF OCRACOKE ISLAND. 



Leaf anatomy of salt-marsh species — Continued, 



[Tim si^u X indicates presence of character; + its imperfect development.] 





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1 Characters given under species of the "sand strand," p. 389. 



GEOGRAPHICAL AFFINITIES OF THE FLORA. 



According to its geographic position, Oeracoke Island lies well 

 within the Austroriparian area of the Lower Austral life zone in North 

 America. 1 For two reasons, however, this relationship of its flora is 

 somewhat obscured: (1) By the large proportion of strand species, 

 many of which have a very extensive geographic range; and (2) by the 

 absence of many of the most characteristic species of the Austro- 

 riparian area, due to the peculiar physical environment. 



Of the total number of species of embryophytes (about 135) collected 

 or observed upon Oeracoke Island, between one-fourth and one- third 

 may be designated as maritime, i. e., normally occurring only in the 

 salt marshes or on the sand strand bordering the ocean. Those may 

 be segregated into 4 groups, according to geographical range: 



1. Species occurring also on the coasts of tropical America. 



A prefixed asterisk (*) indicates that the species does not extend 

 north of the mouth of Chesapeake Bay; a prefixed dagger (f) that 

 the northern limit is in North Carolina, probably not far from Oera- 

 coke. Triglochin striata and Monniera monniera extend north to 

 eastern Maryland. 



1 Merriam, Geogr. Diatrib. p. 211; Life Zones p. 45, map. 



