128 Rhodora [May 
In the following lists given for the different formations the nomenclature 
of Gray’s Manual, 6th edition, is mainly followed and also in general the 
same specific limits. Trees are starred (*) and shrubs marked thus (°), while 
the species characteristic of the different formations are étalicized. 
1. SAND-BARREN FORMATION.  XeropAytes. 
Habitat: dry sand hills, drifting sands, and open sandy fields and 
plains, where the common species fail to maintain a foothold; flora 
well-marked but rather local, except in the Cape Cod region ; species 
few and characteristic. Passes into (3) and (7). 
Hudsonia tomentosa, Nutt. Krigia Virginica, Willd. 
H. ericoides, L. Aralia hispida, Vent. 
? Arctostaphylos Uva-ursi, Spreng. Aster linariifolius, L. 
Lechea minor maritima, Gray. Lechea thymifolia, Michx. 
9 Ilex glabra, Gray. ? Myrica cerifera, L. 
Hypericum nudicaule, Walt. Spiranthes simplex, Gray. 
Cyperus filiculmis, Vahl. ? Smilax rotundifolia, L. 
Chrysopsis falcata, EN. Corema Conradii, Torr. 
Cyperus Grayit, Torr. Lechea tenuifolia, Michx. 
2. HILLTOP-BARREN Formation, Xerophytes. 
Habitat: high points of slate or granite exposed by denudation, or 
cliffs; very local; passing into (4). 
° Quercus prinoides, Willd. Cardamine parviflora, L. 
9 Q. ilicifolia, Wang. Polygonum tenue, Michx. 
* Juniperus Virginiana, L. Aster linariifolius, L. 
9 7. communis alpina, Gaud. Aristida dichotoma, Michx. 
9 * Prunus Pennsylvanica, L. f. Corydalis glauca, Pursh. 
? P. cuneata, Raf. Krigia Virginica, Willd. 
? Arctostaphylos Uva-ursi, Spreng. Houstonia purpurea longifolia, Gray. 
? Rhus typhina, L. ? Vaccinium Pennsylvanicum, Lam. 
* Pinus rigida, Mill. Ranunculus fascicularis, Muhl. 
Silene Pennsylvanica, Michx. Lespedeza capitata, Michx. 
Viola pedata, L. Andropogon scoparius, Michx. 
V. ovata, Nutt. Selaginella rupestris, Spring. 
Aralia hispida, Vent. *° Prunus Virginiana, L. 
Lechea tenuifolia, Michx. 
More frequent on the cliffs : 
Saxifraga Virginiensis, Michx. Woodsia ilvensis, R. Br. 
Aquilegia Canadensis, L. Asplenium Trichomanes, L. 
° Rhus Toxicodendron, L. Polypodium vulgare, L. 
