156 College of Forestry 
Thus we have a further illustration (noted already in case 
of bog formation) of the tendency of identical edaphic condi- 
tions to choose — if an environment may be said to choose — 
or control the selection of identical ecological vegetation units. 
Just what the edaphic factors are and how they operate (1. e. 
whether it is water deficit, lack of available food, acid re- 
action, or all these that determine the xerophytic aspect of the 
vegetation) should be determined by further comparative 
studies. In this connection, the existence of this vegetation 
type on barren mountain tops and slopes suggests that at any 
rate it 1s not a question of deep sand beds. Thus, what ap- 
pears to be the ecological equivalent of the coastal and delta 
pine barrens occurs on the summit of the Shawungunk 
Mountains’ where pitch pine, dwarf chestnut oak, heath 
shrub and other elements of the pine barren flora, indicate the 
pine barrens type of vegetation. ‘The conditions prevailing 
on the Oneida Lake sand flat where Polytrichwm and leather 
leaf are dominant and on “ The Plains ” where lichens and 
Polytrichum constitute (in October) the chief ground cover, 
suggest an interesting comparison with the pine barren and 
heath formations of northern Germany.’ 
The Resemblance Between Heath-Bog and Pine Barrens 
Vegetation. 
In the list of plants which have been given as indicative of, 
or the controlling elements in bog and sand barren vegetation 
it has come out that some of the very striking species occur in 
both situations. Thus, leather leaf (Chamaedaphne caly- 
culata which is the main species of the heath shrub cover of 
the Phoenix bog is also equally abundant on the Oneida Lake 
sand flat. It is reported also among the sand barren group of 
1 Britton, N. L., Bull. Torr. Bot. Club., XI:125, and XIV:187. Harsh- 
berger, J. W. Phytoeogr. Surv. of No. Amer., p. 475. 
2Graebner, Paul, Allgemeine Pflanzengeographic, 1910, p. 277, says 
that the vegetation of ‘ niihrstoffarmen Siinde”’ may be sparse grasses 
or dwarf (heath) shrubs, but the “ hauptrolle” is played by Polytric- 
hum piliferum, Rhacomitrium and lichens, especially Cladonia species. 
