Too BOTANICAL GAZETTE [| AUGUST 
invitation to colaborers. There is no special reason for exclud- 
ing eastern Texas from this discussion, other than that the whole 
field is too large for a single paper. During a residence of 
more than three years, the writer has personally explored a 
great deal of the state, and yet there are vast areas he has not 
seen, and of which he cannot speak from first-hand knowledge. 
Hence even this general analysis of the vegetation must contain 
inaccuracies and misjudgments, which only a detailed survey of 
the provinces concerned will correct. 
With the opportune appearance of Professor Hill’s Physical 
geography of the Texas region* the task of presenting the climatic 
and especially the physiographic and geological factors has been 
much lightened, and by his courtesy a very free use has been 
made of this Texas folio. He has given much help also in the 
way of suggestions and photographs, which is herewith grate- 
fully acknowledged. Dr. V. Havard’s Report of the botany of 
southern and western Texas* has also been of great service. 
The order followed is to discuss first the climatic factors in 
their relation to the vegetation of the region, and second the 
vegetation itself under several general types of association 
(plant formations), together with the factors of geology, soils, 
and physiography (edaphic factors), which determine chiefly 
the type of formation upon any given area. Omitting from con- 
sideration practically all of the Texas region lying to the east of 
meridian 97°30’, we have to deal with an area covering in its 
greatest north-south dimensions 10.5° of latitude (from about 
26° to 36.5°), a fact of no small significance in climatic zones; 
and in its east-west extent 9° (from 97.5° to 106.5°), a distance 
sufficient to carry the western border into the Pacific zone. - 
CLIMATIC AND EDAPHIC FACTORS. 
TEMPERATURE, 
In the facts that the southernmost point of Texas is at sea 
level and borders on the Gulf, and is but 26° north of the equator; 
*U. S. Geological Survey. Texas folio. 1900. 
? Proc. U. S. Nat. Mus. 8: —. 1885. 
