1919] 



VESTAL— PHYTOGEOGRAPHY OF COLORADO 



169 



meeting of two such ravines, are common. Older buttes are 

 fewer and more distant from one another. 



Figs. 9, 10— Buttes and plateau areas: fig. 9, North Table Mountain at Golden, 

 west of Denver; this and South Table Mountain are capped with basalt; fig. 10, 

 Fisher Peak, northern end of Raton mesas, as seen from valley of Purgatoire River, 

 a few miles above Trinidad; upland in midground belongs to southern sedimentary 

 plateau; vegetation is principally dry grassland with scattered pinyons and cedars 

 and infrequent clumps of scrub oak. 



The plateaus and buttes are found outside of the upturned ridge 

 and valley zone wherever the surface rocks are rather resistant. 

 These resistant strata are usually the most recent and uppermost, 



