Mammillaria 1a Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria 2a Lund Bot Garden 150503 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria 2b Lund Bot Garden 150503 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria 2c Lund Bot Garden 150503 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria 3a Lund Bot Garden 150422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria bocasana Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria bombycina Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria bombycina Lund Bot Garden 140331 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria carnea Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria compressa 1 Copenhagen Bot Garden 160504 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria compressa 2 Copenhagen Bot Garden 160504 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria compressa 3 (cult) Puertito de Güímar, Tenerife 160405 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria compressa 4 (cult) Puertito de Güímar, Tenerife 160405 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria compressa 5 (cult) Puertito de Güímar, Tenerife 160405 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria decipiens 1 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria decipiens 2 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria densispina Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria elongata 'copper king' 2 (cult) Lund Sk 160503 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria elongata 'copper king' 3 (cult) Lund Sk 160503 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria elongata Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria geminispina 1 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria geminispina 2 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria geminispina 3 Copenhagen Bot Garden 160713 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria gigantea 1 Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria gigantea 2 Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria gracilis Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria guelzowiana 1 Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria guelzowiana 2 Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria guelzowiana 3 Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria hahniana 1 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria hahniana 2 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria hahniana 3 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria hahniana 4 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria hahniana 5 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria hahniana 6 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria hahniana 8 Copenhagen Bot Garden 160504 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria heyderi ssp gummifera Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria karwinskiana 2 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria longimamma 1 Lund Bot Garden 100519 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria longimamma 3 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria longimamma 5 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria longimamma 6 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria longimamma 7 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria magnimamma 1 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria magnimamma 2 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria magnimamma 3 Lund Bot Garden 140422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria magnimamma Lund Bot Garden 100519 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria parkinsonii 1 Lund Bot Garden 070625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria parkinsonii 2 Lund Bot Garden 070625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria prolifera 1 Lund Bot Garden 140331 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria prolifera 2 Lund Bot Garden 140331 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria prolifera 3 Lund Bot Garden 150422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria prolifera 4 Lund Bot Garden 150422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria prolifera 5 Lund Bot Garden 150422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria rhodantha 1 Lund Bot Garden 070625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria surculosa 1 Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria surculosa 2 Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria uncinata Botan, Stockholm 020514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria wildii 1 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria wildii 2 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria wildii 3 Lund Bot Garden 150422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria wildii 4 Lund Bot Garden 150422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria 1b Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria cf dioica 1 SW La Quinta, CA 130417 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria cf dioica 2 SW La Quinta, CA 130417 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria elongata 'copper king' 1 (cult) Lund Sk 160503 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria hahniana 7 Copenhagen Bot Garden 160504 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria karwinskiana 1 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria longimamma 2 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria longimamma 4 Lund Bot Garden 130531 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Mammillaria rhodantha 2 Lund Bot Garden 070625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).