118 Rhodora [Jury 
comparison with the ample material at Philadelphia. On May 12, 
1918, Mr. Edgar Brown, Prof. A. S. Hitchcock, Mr. Maxon, and the 
writer visited the Suitland bog and found the plant growing in some 
abundance. It was not very conspicuous, however, for the plants 
were scattered and half hidden among tufts of withered grass. 
The two other species of Senecio common about Washington are 
found in quite different habitats. S. aureus is frequent along streams 
and in wet soil generally in the hilly Piedmont Region westward, 
especially along the valley of the Potomac. ` 5. Smallii, also, occurs 
in the same general region, but in dry, elevated situations. S. Craw- 
fordii, on the other hand, occurs in one of the characteristic white 
gravel or magnolia bogs of the low C oastal Plain. — 
These bogs are the most interesting feature of our local flora.' 
They are small, hardly more than a few yards across, and lie always 
upon a gentle slope, usually surrounded by a thick growth of trees 
and shrubs, a circumstance which often makes their discovery difficult. 
'The necessaty condition for their occurrence is a thin bed of gravel 
or coarse sand, commonly about a foot thick, lying between two beds 
of clay. On a hillside where the gravel is exposed the water which 
flows through the subterranean gravel stratum trickles over the bed 
and keeps it constantly wet, even in the driest seasons. Such bogs 
are very pleasant botanizing grounds, for here one may wander about 
nearly dry-shod among.a host of interesting bog plants which usually 
grow in much less comfortably accessible places. A number of the 
bogs are known in the Coastal Plain region north and east of Wash- 
ington, and there are probably others still undiscovered in the less 
explored portions of our area. "They are our only stations for a num- 
ber of interesting species, most of which are characteristic pine-barren 
plants. The bog near Suitland is in some respects the most interest- 
ing of all, for it has yielded several species not found in the others 
within our limits? such as Carex Collinsii, Habenaria cristata, Polygala 
lutea, and Arethusa bulbosa. The last species was reported from our 
region about 80 years ago, but had not been recollected until we dis- 
covered it near Suitland at the same time that we collected the Senecio. 
1See W. L. McAtee. A sketch of the natural history of the District of Columbia. Bull. 
Biol. Soc. Washington i. 74-90 (1918). McAtee gives a very full and interesting account of 
the magnolia bogs, and an equally instructive discussion of the other phytogeographic features 
of the District and vicinity. 
2 The area included in the District flora region, as usually limited, is a circle of 15 miles radius, 
the Capitol being taken as the center. 
