‘390 Part IV. Chapter 2. 
Hill Top Barren Formation. Where high points of slate or granite are 
exposed by denudation, a characteristic formation occurs. Sometimes this 
formation (usually local) is found on rocky cliffs. The trees which grow in 
the ledges are in dry soil under xerophytic condition, consequently the number 
of arborescent species is small. Ouercus prinoides, O. iicifolia, Funiperus 
virginiana, 7. communis var. alpina, Prunus pennsylvanica, P. virginiana and 
Pinus rigida comprise the list of trees occuring in such places associated with 
Vaccinium pennsylvanicum, Rhus typhina etc. 
Sand Plains Formation. Certain sand plains near North Haven, Connec- 
ticut are covered with a xerophytic vegetation composed of Andropogon scopa- 
rius (in tufts), Cyperus filiculmis, Sporobolus, Syntherisma, T' richostema, Poly- 
gonella, Hypericum nudicaule, Asclepias Cornuti (syriaca), Baptisia, Helianthemum, 
Artemisia caudata. — Juniperus virgimiana, $. communis, Prunus serotina, 
Quercus tinctoria var. are the dominant trees and grow in scattered groups 
while certain areas are covered with C/adonia rangiferina and C omptonia aspleni- 
foha (= C. peregrina'). 
' The sand plains in Vermont”) are characterized by trees and shrubs of 
Prunus cuneata, Pinus rigida, Quercus ilicifolia (= 0. nana Sarg.), Salix 
humilis, clumps of the dominant grass Andropogon nutans var. avenaceus 
(= Chrysopogon avenaceus Michx.) with Carer Houghtonii, Mühlenbergii, siccata 
and Fimbristylis capillaris and many perennials, such as Asclepias obtusifolia, 
Solidago puberula, Aster linarüfolius, Lespedeza capıtata, Lupinus perennis, 
Helianthemum majus, Viola arenaria and Spiranthes gracilis. 
B. Lake District. 
This phytogeographic district occupies the region west of Lake Champlain 
and the Ottawa River representing the drainage basin of the Great Lakes, 
with its northern boundary indicated approximately by the northern limit 
of white elm, Ulmus americana. It stands midway between the deciduous 
forests of the central eastern United States and the subarctic forest on the 
north and possesses enough of characteristic plants to separate it from the 
Maritime District on the east and the Prairie Region, which limits it on the 
west. Two areas are sufficiently distinct to merit recognition. These are know 
respectively, as the Interlacustrine and Adirondack areas. 
a) Interlacustrine Area. 
This area comprises the country immediately surrounding the Great lakes 
and other glacial lakes west of the Ottawa River. 
ı) Brirton, Wırrox E.: Vegetation of the North Haven sand Plains. Bulletin Torrey Botanical 
Club XXX: 571. 
2) BRAINERD, EzrA, Jones, L.R. and E6GLeston, W, W.: Flora of Vermont. Contributions 
to the Botany of Vermont VIII: 100. 900, 
