14 FOREST RESOURCES OF TEXAS. 



TEMPERATURE. 



On the whole, the trees which compose the forests of Texas arc those 

 characteristically found in the southern part of the United States. The 

 presence of palmetto, magnolia, live oak, longleaf and loblolly pine, 

 and the mimosas attest this. On the other hand, not only do many 

 species of the forests of the Middle States and even of the North 

 Atlantic States occur, and indeed extend almost to the Gulf such as 

 hornbeam, ironwood, river birch, beech, and black walnut, with cer- 

 tain of the hickories, ashes, and oaks but in the Guadalupe Moun- 

 tains, where the State reaches its greatest altitude of 9,500 feet, there 

 also appear the western yellow pine and red fir, species characteristic 

 of the Pacific Northwest. Along these lines temperature is the domi- 

 nant selecting agency. 



SUNLIGHT. 



The area of Texas presents extremes in the amount and intensity of 

 sunshine which are reflected in the character of the forest growth. 

 Thus, in the eastern forest area the most intense illumination is pre- 

 vented by the blanket of moist atmosphere, and the duration of it is 

 limited by the high percentage of partly or wholly cloudy days. In 

 this area develop thick-crowned hardwood forests, having a lieuvy 

 undergrowth of shade-loving species. In the Kio Grande country, on 

 the contrary, the sun beats down with great intensity during the 

 growing season, and its force is little weakened by the extremely dry 

 air and the continuously unclouded sk}^ The trees which have been 

 favored by this condition of light and dryness have a meager foliage, 

 such as mesquite and the acacias, which hardly break at all the direct 

 force of the sun's rays and give insufficient shelter to less intolerant, 

 to s&y nothing of s.hade-loving, species. Except in moist canyons and 

 on alluvial bottoms, the Texas region west of the ninety-seventh 

 meridian is conspicuously wanting in shade-loving trees, and in fact 

 in shade-loving vegetation of all kinds. 



In contrast with the thick-crowned hardwood forests of east Texas 

 are its characteristically open stands of longleaf pine, itself intolerant 

 of shade, and entirely destitute of an undergrowth of shade-loving 

 species. 



WINDS. 



The wind plays its role chiefly in hindering the encroachment of 

 timber. Its power in this direction will be better appreciated when a 

 more general attempt is made to start tree plantations on the open 

 prairie. Orchardists in the Gulf region realize what the Gulf breeze 

 is to contend against, and their orchards record the battle. In the 

 coast region and on the Staked Plains the habitual direction and force 



