He was from Texas an' them Texas boys jus' naturally thought as how he'd saddle up an' ride right 'long wi' 'em.
The Texan boys mocked him because he was from Missouri. 
mnli hypothesis: The Texan boys mocked him because he was from Missouri.  premise: He was from Texas an' them Texas boys jus' naturally thought as how he'd saddle up an' ride right 'long wi' 'em.