1903] FLORA OF NORTH CAROLINA 381 
inverse proportion to the presence of fresh well-aerated humus. 
Does not this circumstance seem to imply that there must be 
some causal connection between the quality of the humus and 
the occurrence of xerophytic characters? The presence of such 
plants as Xerophyllum asphodelioides, Paronychia argyrocoma, 
Chrosperma muscaetoxicum on the summit of Grandfather 
Mountain, and Dendrium on both Grandfather and Roan Moun- 
tains seems thus to be explained. 
SUB-ALPINE TREELESS FORMATION, 
This formation is encountered typically on Roan Mountain 
and on other mountain summits in the southern Appalachians 
that are grassy balds. The “balds” are in the main grassy 
meadows, but the rounded domes show extensive areas covered © 
by the Rhododendron catawbiense (R. catawbiense Association) , 
either pure, or associated with Alnus alnobetula (Adnus Assocta- 
ton). The alder covers an adjoining dome of the Roan Mountain 
Range, the Elkhorn, with a pure and impenetrable growth three 
to four feet high, The extent of the rhododendron thickets, for 
which the mountains is famous, cannot easily be estimated. The 
bushes may be either rounded, like a hay stack, or they may be 
spreading at the top.3%° The character of the plants, as indicated 
by the general habit and nature of the leaves, depends upon 
whether the plants are exposed to the cold winds of summer, the 
intense sunlight, the icy blasts of winter, or whether they are 
more or less sheltered by the slope of the ground, or by growing 
beneath the protection of the spruces and silver firs. 
The summit of Roan Mountain is in the form of a saddle 
several miles long, being formed of two elevations of about equal 
height, the culminating peak being 6,313 * (1,924™) in altitude. 
The component vegetation of the grassy meadows, or ‘‘balds” 
consists of Trifolium repens, Rumex acetosella, Potentilla cana- 
densis, Poa compressa, Veronica officinalis, Houstonia serpyl- 
lifolia, Carex tenuis, Deschampsia flexuosa, Luzula campestris, 
and Phleum pratense (Carex-Poa Association). Polytrichum com- 
a 3 CANNON, W. A., Field notes on Rhododendron Catawbiense. Torreya 
2:161. rgo02. 
