Don't worry! The small dark spots in the epidermis of some Gymnocalycium species of the subgenus Muscoseminueum (e.g. G. mihanovichii, G. friedrichii, G.megatae, G. schickendantzii) are characteristic for these plants. It is not a disease or a pest.

A good find! The download of this book and many, many more books and journals is provided by the digital library of "Au Cactus Francophone": https://www.cactuspro.com/biblio/en:accueil (Thanks to Daniel!) The link has already been mentioned here in the forum, but it is worth pointing out a...

The plant on the second picture is not Gymnocalycium capillaense, but a more or less young, damaged specimen of Gymnocalycium valnicekianum. The arrangement of the spines is quite characteristic.

fatich wrote: ↑Wed Jul 15, 2020 8:41 pm

Aiko wrote: ↑Wed Jul 15, 2020 7:05 pm You are fast to find it in the trade. Where did you get those?

I acquired the seeds last year when i was in Mexico.

Did you get a Mexican export permit (CITES), which is necessary for the export of cactus seeds from Mexico?

My suggestions:
1 Gymocalycium calochlorum (probably not G. bruchii)
2 Parodia sp. (microsperma?), as already discussed
3 Gymnocalycium achirasense (or G. horridispinum)
6 Mammillaria bocasana (obviously the red flowering cultivar, which was created in the German cactus nursery Haage in the 1970s)

In recent years I have received several thousand portions of seeds from various seed traders, cactus friends or the German cactus society. It is the exception that seed portions are incorrectly labeled, but it happens. I have even received seeds from other plant families as a big exception in allege...

Ali Baba wrote: ↑Sat Mar 09, 2019 12:33 pm Monanthes polyphylla

A wonderful picture that clearly fits the theme of "beautiful mathematical forms". The picture reminds me of the Brassica variety 'Romanesco', whose fractal patterns every mathematician should enjoy.

NickHitchcock wrote: ↑Mon Mar 25, 2019 10:12 pm Detlev they are brilliant photos, did you stack and stitch them yourself?

Yes, I made the photos myself with the focus stacking method. I'm glad you like the pictures.

Here are some pictures -- perhaps less mathematical, but clearly patterns! So that no one has to puzzle: these are seed surfaces of cactus seeds. Escobaria vivipara Escobaria__vivipara.jpg Ancistrocactus uncinatus Ancistrocactus_uncinatus.jpg Stenocactus lloydii Stenocactus_lloydii.jpg Pilosocereus ...

Ralph Martin is right. The plant belongs to that group (Gymnocalycium subgenus Muscosemineum). It is a form of G. anisitsii (or G. damsii if you prefer). It is not G. friedrichii or G. mihanovichii. It is not easy to describe how to identify them. It is the flower and the stem (ribs, spination), but...