on coarse gravels of dark basalt at base of roadcut for new highway across the Sa. La Brena escarpment that largely obliterated the old, one lane railroad bed that provided access to the botanically rich, exciting and very scenic climb into the Madrean highlands
part of the Mentzelia key refers to petaloid filaments which you can see here. Between the five large petals are petaloid filaments with anthers at their tips!