THE ECOLOGICAL RELATIONS OF THE VEGETA- 
TION OF WESTERN TEXAS. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORA- 
TORY... AX: 
WILLIAM L. BRay,. 
(WITH TWENTY-FOUR TEXT FIGURES) 
[Continued from p. 123.] 
THE GREAT PLAINS. 
THIS great region is naturally divided into two sub-regions, 
(1) the prairie plains, from which, except for scattered rem- 
nants, the original Great plains deposits have been removed, and 
embraced in the central and east central provinces of Hill 
(fig.1); and (2) the remaining areas of Great plains proper 
(Llano Estacado, Edwards plateau, and Stockton plateau). 
The prairie plains.—This sub-region embraces the grass coun- 
try of central and north Texas west of meridian 97.5°, an area 
Over 50,000 square miles in extent. As previously stated, it is a 
vast region of denudation, presumably from a former plain which 
must have stood at a much higher level. Whatever may have 
been the overlying formations, the present stage of erosion pre- 
sents exposures of various formations, each of which owes its 
individuality chiefly to the character of the strata now undergo- 
ing reduction. Taken as a whole the dominant vegetation is a 
grass formation, but upon the areas of sand and gravel exposure, 
and the hills, bluffs, and streamways, timber formations prevail. 
The provinces are the Grand prairie and those of the central 
denuded region; embracing (1) the granite country, (2) the Car- 
boniferous area (Brownwood and Palo Pinto countries), (3) the 
upper cross timbers, (4) the red beds country, and (5) the Cal- 
lahan divide. 
THE GRAND PRAIRIE— Geologically this is a Lower Creta- 
ceous area extending from the Colorado river (its eastern 
Igor] 195 
