harper: PHYTOGEOGRAPHY of southern MARYLAND 583 



indicated by the letter E, and the percentage of them for each 

 region has been estimated, for that seems to be a good index of 

 soil fertility. Common names are added for the benefi of 

 nonbotanical readers who may have occasion to explore some of 

 the same territory. 



The plant lists include only native forest trees large enough to 

 be sawn for hmiber, those being the most conspicuous and 

 important components of the vegetation. If smaller trees, such 

 as the dogwood, were included it would be difficult to compare 

 them with the larger ones with respect to abundance, and very 

 little additional contrast would be gained thereby, for it happens 

 that the dogwood is the commonest small tree in all five regions 

 (as well as in many other parts of the eastern United States). 

 A few notes on shrubs and herbs are added, but to attemptto 

 list those would require entirely too much space for the limits 

 of this paper. The names of trees seen only a few times in a 

 given region are omitted, because of the possibility of their 

 having been wrongly identified, or not properly belonging to the 

 region. 



1. THE FALL-LINE CLAY HILLS 



This corresponds approximately with the region of the non- 

 marine Lower Cretaceous formations (Potomac group), which 

 form a belt averaging seven or eight miles wide adjacent to the 

 fall line all the way across Maryland and the District of Co- 

 lumbia and a little way into adjoining states. It is analogous 

 in many ways to the fall-line sand hills of the Carolinas and 

 Georgia, and some of its features, particularly the mottled clays 

 and ferruginous sandstones, are matched very closely in a belt 

 just below the fall line in Alabama. It is most typically devel- 

 oped between Washington and Baltimore, where it occupies all 

 the country between the Baltimore & Ohio Railroad and the 

 Washington, Baltbnore & Annapolis electric line, and a little 

 more on either side. 



The underlying strata, exposed in innumerable cuts, consist 

 of pinkish or mottled stiff clay, more or less mixed with sand 

 and gravel, and the soils are mainly sandy and gravelly loams, 

 all distinctly acid or noncalcareous. The surface is strewn in 



