Although this photo is overexposed, the remarkable row of long spines down the midrib on the lower surface of a Codon royenii leaf are clear to see. Between the spiny margins and the prominent midrib, the blade is smooth apart from some notable lateral veins.

Smaller spines on the stem vary in a range ending in what may be no more than large hairs (Le Roux, et al, 2005; Leistner, (Ed.), 2000; Eliovson, 1990; iNaturalist; Wikipedia; http://pza.sanbi.org).