Examples of coastal Species. 215 
Pine Mountain in northwest Georgia, also in Alabama on the southern slopes 
of Horseleg and Head mountains, while there are several other species such 
as Quercus Iyrata, O. Michauxii, Magnolia glauca, Iex glabra, Nyssa uni- 
flra with equally interesting distribution. On the southern slope of Pine 
Mountain on the other hand associated with Pinus palustris are Pinus echinata, 
Andropogon scoparius, A. virginicus, Aletris farinosa, Quercus marylandica, 
©. prinus, Tephrosia (Cracca) virginiana, Ceanothus americanus, Viola pedata, 
Eupatorium album, Chrysopsis graminifolia, Solidago odora, Sericocarpus lini- 
Folius, Silphium compositum, Helianthus divaricatus, all but one two of which 
are common to the dry pine barrens of the coast plain. 
The action of the several uplifts and depressions of the earth’s surface was 
‚most profound upon the vegetation of this coastal plain. With every sub- 
mergence of the lower portions of the region, the vegetation in the area of 
submergence was destroyed, or if existing on the higher grounds, was sub- 
jected to such extensive changes of level, as to highly modify its character 
and the distribution of the component species. We have, however, data on 
the origin of a number of the elements of the coastal plain flora which is here 
apropos. On the coastal plain of the southeastern North America we have 
the following species of the genus Yucca: Yucca filamentosa var. vera, Yucca 
JHlamentosa var. concava, Yucca filamentosa var. bracteata, Yucca filamentosa 
var. patens, Yucca gloriosa, Yucca aloifolia, Yucca recurvifolia, all ranging 
east of the Mississippi River. West of that river, we have along the Red 
River, Yucca louisianensis, Yucca arkansana, in southern Texas, Yucca Schottii. 
The Mexican tableland is perhaps the original home of the entire group of 
Yuccas and the eastern species have taken a sweep around the gulf coast 
with a possible reflex wave northwest into the Appalachians. Yucca aloifolia 
perhaps a derivative of the Central American Y. elephantipes reached the coastal 
plains through the West Indian islands, for according to TRELEASE it seems 
to have evolved there. It is possibly a later introduction than the other species, 
as it is found on the newer parts of the coastal plain, viz., the Mississippi 
delta and the sand dunes of eastern Florida and Georgia. The fact also that 
so many varieties of the species filamentosa are recognizable, favors the view 
which the writer has all along held that a plant entering new country and 
subjected to different conditions is likely to undergo mutation. These plants 
reached the coastal plain in post glacial times, or not earlier perhaps, than 
the late Tertiary period. 
The strand plants of the delta of the Mississippi River‘) some of them of 
tropic, or subtropic distribution are the following, the New World species 
being left unmarked, while the circumterrestrial are marked by an asterisk: 
Batis maritima L. | *Avicennia nitida Jacq. (= A. littor- 
Canavalia obtusifolia DC. | alis Boiss.) — 
1) Bu Francis E. and Tracy, $S. M.: The insular Flora of Mississippi and Louisiana. 
Bulletin Torrey Botanical Club XXVI: 61—ı01. March 1901 
