those obviously collected outside of the above-described area. All of the 

 collectors, including the present writer, have deposited specimens with the 

 National Herbarium of the Smithsonian Institution or with the Herbarium 

 of the United States National Arboretum. Since preparation of the manuscript, 

 the inclusion of several plants hitherto omitted has resulted from the sugges- 

 tions of P. L. Ricker, President, Wildflower Preservation Society, as a result 

 of his familiarity with plants of the Washington district and the Arboretum. 

 A few plants of special interest growing only just outside the Arboretum 

 property lines will be mentioned in the list with appropriate notation. For 

 convenience of reference, botanical nomenclature follows that of the eighth 

 edition of Gray's Manual of Botany. 



The locations referred to by number in these notes are indicated on the 

 accompanying map (fig. 1). They are taken from a more accurate grid survey 

 prepared by the writer in 1950, which is available for reference purposes at 

 the Arboretum. 



EQUISETACEAE 



Equisetum arvense L Common horsetail. 



Occasional, locations 55 and 28. 



LYCOPODIACEAE 



Lycopodium complanatum var. flabelliforme Fern. 



Groundcedar, groundpine. 



Occasional in thickets having a moist acid soil. 



OPHIOGLOSSACEAE 



Botrychium dissectum forma obliquum (Muhl.) Fern Grapefern. 



Rare, found in locations 12 and 45. This species matures its spores in 

 autumn. 



Botrychium virginianum (L.) Sw.. Rattlesnakefern. 



Frequent in thin woods. 



Ophioglossum vulgatum L Adderstongue. 



Rare, not found in recent years. 



OSMUNDACEAE 



Osmunda cinnamomea L Cinnamonfern. 



Frequent in wet soil. Conspicuous on steep banks that are springy. 



Osmunda claytoniana L Interrupted-fern. 



Steep bank near river, location 46. 



Ownunda regalis var. spectabilis (Willd.) Gray Royalfern. 



Rare, found in wet soil. 



3 



