Euphorbia cooperi stem tip seen from above

This photo taken of a Euphorbia cooperi stem from above shows how thin the stem blades or wings may be. In this case there are just two opposing pairs, positioned perpendicularly to each other, resembling the propeller of a weird, old-fashioned aeroplane.

The greenish yellow cyathia buds on the spine shields are halfway between the pairs of angled spines that appear like cattle horns, their tips outwardly angled and tapering.

The colour change from purple to pale grey of the continuous hard ridge that is the spine shield occurs rather quickly on the new growth. The spine tips are last to change colour (Smith, et al, 2017; Coates Palgrave, 2002; Schmidt, et al, 2002; Pooley, 1993; iNaturalist).