Chamaecereus silvestrii (ref.)
Spegazzini's first description can be seen in Roberto Kiesling's compilation of Spegazzini's publications in the cactuspro Cactus and Succulent Digital Library.
Although well-known in cultivation, this is one of the few cacti thought to be extinct in its original habitat (or, at least, its habitat has not been rediscovered in ~110 years of searching). Most of the material in cultivation seems to be of a single clone that has been propagated vegetatively. At least two other lines do exist, however: DH 301b plants have come to cultivation via Dietrich Herzog who received his plants from a man who had collected them in the northern part of the Cumbres Calchaquíes and ES 73 plants which come from two clones collected by Eberhard Scholz from the walls of the cemetery in Colalao del Valle, Tucumán. Seedlings raised from the ES 73 plants are unlike their parents, and have shorter, thicker stems and prominent upcurled central spines. Their fascinating story along with photos can be seen in Freundeskreis Echinopseen Informationsbrief, again, in the cactuspro Cactus and Succulent Digital Library.
Although well-known in cultivation, this is one of the few cacti thought to be extinct in its original habitat (or, at least, its habitat has not been rediscovered in ~110 years of searching). Most of the material in cultivation seems to be of a single clone that has been propagated vegetatively. At least two other lines do exist, however: DH 301b plants have come to cultivation via Dietrich Herzog who received his plants from a man who had collected them in the northern part of the Cumbres Calchaquíes and ES 73 plants which come from two clones collected by Eberhard Scholz from the walls of the cemetery in Colalao del Valle, Tucumán. Seedlings raised from the ES 73 plants are unlike their parents, and have shorter, thicker stems and prominent upcurled central spines. Their fascinating story along with photos can be seen in Freundeskreis Echinopseen Informationsbrief, again, in the cactuspro Cactus and Succulent Digital Library.