proceedings: botanical society 435 



sisted of A. S. Hitchcock, Agnes Chase, and J. H. Painter Early in 

 1915 Frederick V. Coville and A. S. Hitchcock undertook to organize 

 a study of the District flora on the cooperative basis and the plan was 

 reported to the Society in 19*15. During 1915 and the early months 

 of 1916 keys of nearly all the families were prepared. These keys were 

 mimeographed and distributed to contributors. Mr. Coville has since 

 withdrawn from active leadership and the flora is now under the direc- 

 tion of Mr. Hitchcock and Mr. P. C. Standley. A total of twenty- 

 five contributors are at work on the different groups. A preliminary 

 manuscript is to be turned in by June 1 and the manuscript completed 

 by November 1 of this year. 



Mr. Edgar T. Wherry, at the invitation of the Society, gave a paper 

 on Geological areas about Washington. Mr. Wherry not being able to be 

 present, the paper was read by Mr. Hitchcock. The most prominent 

 geological feature is the Fall Line, which separates the Piedmont Plateau 

 on the northwest from the Coastal Plain on the southeast. This line 

 was named from the fact that the rivers and smaller streams flowing 

 southwestward toward the sea often have waterfalls or rapids at or 

 near this line. Above this the valleys are narrow and steep-sided and 

 the contour lines close together, while below it the valleys are~ broad 

 and open and the contour lines wide-spaced. The geological forma- 

 tions of the Piedmont Plateau are chiefly crystalline gneisses of early 

 periods, among which may be mentioned the Carolina gneiss, granite 

 gneiss, diorite, biotite granite, and basic igneous rocks, including gabbro, 

 nieta-gabbro, and serpentine. The Coastal Plain is occupied by uncon- 

 solidated gravels, sands, and clays deposited during successive ad- 

 vances of the sea during Cretaceous, Tertiary, and Quaternary periods. 

 Gravels also occur to some extent as cappings on the hills along the 

 edge of the Piedmont. Bogs are frequent' in the Coastal Plain and 

 rare on the Piedmont. Lime is present in the soils of the Piedmont 

 through concentration by means of accumulations of leaf mold, al- 

 though there are no highly calcareous rocks in the vicinity. Acid 

 soils are predominant on the Coastal Plain. The speaker called atten- 

 tion to the condition of the flora of the two regions which he illustrated 

 by the distribution of the species of Liliales. Those species limited to 

 calcareous soils found chiefly on the Piedmont Plateau are Allium tricoc- 

 cum, Unifolium canadense, and Trillium sessile. Those limited to noncal- 

 careous or acid soils found chiefly on the Coastal Plain are Aletris 

 farinosa, T afield ia racemosa, and Stenanthium gramineum. The other 

 species grow throughout the region and show no marked soil preference. 



Mr. George B. Sudworth spoke on the subject Distribution of 

 trees in the floral area. Mr. Sudworth traced briefly the history of the 

 study of the trees of the District of Columbia. Lists have been pre- 

 pared at various times by Ward, Knowlton, Holm, and Steele. There 

 are about 400 species and varieties of native and exotic trees growing 

 within the District, many of which are in Government reservations. 

 Of the 140 species of native trees the broad-leaved trees of the District 

 number about 122 species and varieties and are therefore greatly in 



