214 THE PLANT LIFE OF MARYLAND 



area of Baltimore County have an open park-like stand of trees 

 (See Plate XX, Fig. 1). The age of the trees and the absence 

 of seedlings indicates that this is not an early stage in reforesta- 

 tion ultimately giving rise to a more densely closed stand of trees. 

 The Black Jack Oak and the Post Oak are often the sole trees 

 of the thinnest soil, or they may be accompanied by the Red Cedar. 

 The predominance of these two Oaks on the Barrens is one of their 

 most interesting features, for neither of the trees is very common 

 on other soils, although they occur on the sands of the Eastern 

 Shore and on rocky slopes in the Upper Midland District. Infre- 

 quent trees on the thinnest soils are the Sassafras, the White Oak 

 and the Black Oak, while near Gaithersburg the Scrub Pine re- 

 places the Cedar. The scattered shrubs are Vaccinium stamineum, 

 Gaylussacia resinosa, Kalinin latifolia and Salix tristis. The most 

 interesting members of the herbaceous flora are the two species 

 which have not been found off the Serpentine Barrens in the 

 state, — Talinum teretifolium, a small plant with a rosette of terete 

 succulent leaves, and Cerastium arvense* the stems of which have 

 internodes so shortened that the leaves are imbricate in arrangement. 

 In other respects the flora of the thin Serpentine soils is like 

 that of other open xerophilous situations. The areas are not suf- 

 ficiently extensive, nor are the observations which have been made 

 sufficiently full, to give an authoritative list of the species which 

 are absent. Among those which are characteristic of the Bar- 

 rens are: 



Andropogon virgin icus 

 Lechea minor 

 Danthonia sericea 

 Cerastium arvense 

 Heliantliemum ma jus 

 Hieracium sedbrum 

 Aster ericoides 

 Polygala verticillata 

 Potent ilia canadensis 



*In Maryland Cerastium anrmc is confined to the Serpentine Barrens while 

 Cerastium arvense var. oblongifolium is ubiquitous, the reverse relation to that 

 commonly reported. 



