On an old stem of Euphorbia coerulescens the spines assume a daunting appearance, discouraging animals from contemplating juicy bites. But as hunger grows, defences may fail.
The dark, woody rim growing along the vertical ridges is not quite continuous between the angled spine pairs on this plant. The stem shown here has six ridges.
The constrictions on E. coerulescens stems are usually fairly close together as seen in the photo, compared to those found on stems of some other Euphorbia species.