FLORA OF THE DISTRICT OF COLUMBIA. 15 



Cabombaceae, Ranunculaceao, Berberidaceae, Menispermaceae, Papaveraceae, 

 Fumarlacoae, Brassicaceao, Capparidacoao, Sarraooniaceae, Droseraceae, Caesal- 

 piniaceae, Fabaceae, Geraniaoeae, Oxalidaceae, Linareae, Rutaceae, Simarouba- 

 ceae, Limnantbaceae, Impatientaceae, Rbamnaceae, Violaceae, Araliaceae, Corna- 

 ceae, Loganiaceae, Gentianaeeae, Apocynaceae, Boraginaceae, Verbenaceae, 

 Scrophulariaceae, Bignoniaceae, Pinguiculaceae, Acanthaceae, Plantaginaceae, 

 Rubiaceae, Cichoriaceae, Ambrosiaceae, Asteraeeae. 



Tidestrom, I.: Pinaceae, Typhaceae, Vallisneriaceae, Populus, Myricaceae, Jug- 

 landaceae, Betulaceae, Fagaceae, Ulmaceae, Moraceae, Aquifoliaceae, Celastraceae, 

 Staphyleaceae, Vitaceae, Tilia'ceae, Daphnaceae, Diospyraceae, Oloaceae. 



Van Eseltine, Florence L. : Polygalaceae. 



Van Eseltine, G. P.: Alismaceae, Carev, Mentbaceae. 



The following persons aided in the preparation of the preliminary 

 keys: C. V. Piper, P. L. Kicker, P. G. Russell, E. S. Steele, S. C. 

 Stuntz. 



Two keys to families have been prepared, a natural key by Mi 

 Hitchcock (including keys to families of Pteridophyta by Mr. Maxon), 

 and an artificial key by Mr. Standley. The introduction is by Mr. 

 Hitchcock and the glossary by Mr. Maxon. 



The introductory account of the flora of the region is not so full 

 as might be thought desirable. A detailed presentation of the rela- 

 tions of the flora to the vegetation of the surrounding areas, how- 

 ever, is not regarded as essential in a work intended primarily as a 

 classified list of the species. It is hoped that the present volume will 

 stimulate interest in the phytogeography of the region and serve as 

 a basis for an analysis of the flora by those who may have oppor- 

 tunity to study the subject for a longer period. 



The area included by the Flora is approximately a circle of 15 

 miles radius, with the Capitol as the center, this area being prac- 

 tically that of Ward's Flora, though it is not intended to exclude 

 from consideration localities that lie a short distance outside the 

 15-mile circle. The maritime flora of the shore of Chesapeake Bay 

 and of the lower Potomac River is excluded, as is also that of the 

 Patuxent Valley. In the main, the local area reaches to Bowie, 

 Upper Marlboro, and Brandywine on the east, Mount Vernon on 

 the south, Great Falls on the west, and Rockville and Oak Crest on 

 the north. 



The formal list includes all indigenous plants and all introduced 

 ones that have become established. Many species have been collected 

 only once, or sometimes oftener but under circumstances which indi- 

 cate that they are waifs or chance introductions and are not to be 

 considered a part of our flora. Such species are mentioned in notes 

 appended to an allied species or genus. It has not always been 

 possible definitely to determine whether these stray individuals are 

 to be considered a part of our flora, and the decisions in this respect 

 may not be consistent; but rare specimens of species native in this 

 general region may usually be assumed to be indigenous, while those 



