|This specimen is from the Stockton,
area where Bob Ressler lived before he moved to Arizona. This
is one of the varieties he identified on his site, columnar-cacti.org,
as the "true Peruvianus."
But fixing an exact name on these is impossible without some sort of
genetic testing. Someone would have to wander the Andes Mountains
collecting & tagging specimens...
The subtle differences in appearance change with
growing conditions. For example, my specimen shown below is a cutting
that has been rooting over the winter--it has not yet fully "puffed
out" its ribs.
Differences in watering, fertilizing, amount of daily sunlight,
container grown versus in the ground, etc. will all affect appearance.