Natural History of District of Columbia — McAfee 63 



sary to their welfare, as for instance the strand, salt marsh 

 and pine barren plants, or for other reasons never were 

 able to advance from the Coastal Plain to the uplands. It 

 is obvious, therefore, that for reasons of geological history, 

 if for no other, the fall-line must be granted some importance 

 as a faunal and floral boundary. 



Inspection of the remarks upon distribution in the "Plant 

 Life of Maryland" 37 reveals that approximately 163 38 (out 

 of a total of 1,400) species of plants are restricted to the 

 Coastal Plain, while 46 others are chiefly so. Corresponding 

 figures for the Piedmont Plateau are 175 and 48. Search 

 through the local herbarium for the District of Columbia 

 region shows that out of a total of some 1,600 species 193 

 occur only on the Coastal Plain, and 86 others do not extend 

 far upon the Piedmont. Similar statistics for the latter area 

 are 308 and 76. 39 



Thus from 24 to 31 per cent of the plants of Maryland 

 and the District of Columbia region are restricted in dis- 

 tribution either to the Coastal Plain or the Piedmont Pla- 

 teau, and an additional 6 to 11 per cent do not far overstep 

 the boundary of these provinces. 



Lists of the most characteristic or best known species of 

 the District of Columbia region are subjoined. In addition 

 to these most of the species listed further on for Falls 

 Church, Plummers Island, Little Falls and Great Falls also 

 pertain to the Piedmont and those for the Magnolia bogs, 

 and for Beltsville, Odenton, Hollywood, Riverdale, Hyatts- 

 ville, Bladensburg, Penning and Hunting Creek mostly are 

 characteristic of the Coastal Plain. 



37 Special Publication 3, Maryland Weather Service, 1910, 533 pp. 



38 Halophytes are not excluded from this number, since of the 32 listed 

 by Shreve (op. cit. pp. 83-85), 11 reach the Washington area. The reduc- 

 tion in variety of halophytes, as one proceeds from the coast toward the 

 Piedmont Plateau is gradual. If the fall line were farther west 

 some of these plants would range farther in that direction. The distribu- 

 tion of fishes points to the same conclusions. 



38 The figures for the Washington area are incomplete because the col- 

 lections are not entirely worked up. For permission to use the herbarium 

 the writer is indebted to Messrs. W. R. Maxon and P. C. Standley. The 

 unfinished manuscript of the new catalog of the Washington flora also was 

 kindly put at my disposal by Professor A. S. Hitchcock. 



