£903] FLORA OF NORTH CAROLINA 371 
upward. The effect of climatic conditions on the higher 
mountains is more evident than that of soils; though between 
certain limits of elevation changes in the character of the soil 
influence the kind of growth. Thus the location of Rhododen- 
dron maximum and Tsuga canadensis along the mountain 
Streams between certain limits of elevation (climatic) is regu- 
lated purely by edaphic conditions. The growth of Castanea 
dentata, Quercus alba, etc., back from the streams on the hill- 
sides in the drier ground is also edaphic. The presence, there- 
fore, of the various tree species in the mixed forests of the 
southern Appalachians is dependent primarily on climatic influ- 
ences, but the assembling of these species into ecologic plant 
associations in these mixed deciduous forests depends upon the 
edaphic surroundings. With the herbaceous plants of the 
mountain summits and with certain shrubs, their allocation to 
particular situations on these summits is controlled mainly by 
edaphic conditions. Thus Dendrium buxifolium is found grow- 
ing on rock faces and rocky slopes on Grandfather Mountain, 
while on Roan Mountain it is found ina deep soil, rich in humus. 
Xerophyllum asphodelioides, Gaultheria procumbens, Paronychia 
argyrocoma, Geum radiatum, etc., growing on Grandfather 
Mountain are controlled largely in their distribution upon that 
peak by soil conditions. Other examples of this kind of distri- 
bution might be mentioned here, but a more detailed reference 
will be made to the association of species in the forests of the 
higher mountains, when the several regions visited by the writer 
are discussed from an ecologic standpoint. 
It is doubtful, however, if changes of soil in the larger moun- 
tain masses above 5,000 * (1,525 ™) elevation produce any change 
in the kind of trees, the number of species being limited to those 
whose hardiness (xerophytic structure of crown or foliage and 
short growing season) renders them capable of withstanding the 
sudden changes of temperature to which they are subjected near 
the summits of the higher mountains. 
* The word “xerophyte” refers to a particular kind of plant with a definite his- 
tologic structure. The word “ xerophytic” should be used also in the structural sense, 
although by extension it is used loosely to denote conditions that produce xerophytes. 
%®° PINCHOT and ASHE, Timber trees and forests of North Carolina. N. C. Geol. 
Survey 1897 : 208, 209. 
