Mammillaria dioica in the desert

Want to show you some photos from my trip to Anza-Borrego Desert State park, California. It was mid October and not a blooming time of course. I stopped several times along the Hwy 78 and looked for these plants between rocks and dead plants.






This one is branching or dividing?

I saw plants with unripe fruits, it takes half a year or more to htese to ripen.

And many mammillarias hiding in the shade of Ferocactus cylindraceus plants.

Among others I found several of Mam. tetrancistra plants also. One of it was hiding behind a Ferocactus again.





Others two, these close to Cylindropuntia branch, were next to a similar size seedling of M. doica and I did not differed them at first.





There is a green fruit at the bigger one, from the first blooming perhaps.

Nice habitat photos! But could it not be that some of the dioicas from the first set of photos are actually tetrancistras?
I find it difficult to distinguish between them because they are not in flower, tetrancistra should have 30 - 46 radial spines (but in Sonora 18 to 20), dioica 11 - 22 (all according to Pilbeam's book). If I am correct, the Anza-Borrego park harbours both species. The seeds should betray the real tetrancistra, because of the corky appendix.

Wolter ten Hoeve, The Netherlands.

Well, even the main distinguish features of M. tetrancistra (flowers, roots, ripe fruits) were hidden at the time I did those photos, I think I could difference plants of both species found there. M. tetrancistra has several dark, almost black, long but soft hooked centrals per areole and many white radials. The bodies of seedlings I found were soft also. Dioicas I found in that desert had lighter (just upper half was brown) centrals, just one hooked per areole, and mostly less than 15 radials. The bodies staid more robust and fruits had flower remnants at the tips (normally missing at M. tetrancistra's red fruits).

I agree that many features may overlap if taking entire species populations of these two mammillarias. But after some observations, zooming and practice it's possible to determine these two cacti in Anza Borrego. I would go again there in more bloom-likeable time there, even it's different for them, as I already know the localities...

Nice photos, this was one of the first Mamms I saw, Also along HW78, back in 1992. I didn't have long to stop, but I remember the samazement St seeing whole hillsides of Ferocacti. The M. dioica were quite pulled down, but in flower. It was Feb. I may not have recognised M. tetrancistra back then, so will have to check my few colour slides.

Chris43 wrote:

Nice photos, this was one of the first Mamms I saw, Also along HW78, back in 1992. I didn't have long to stop, but I remember the samazement St seeing whole hillsides of Ferocacti. The M. dioica were quite pulled down, but in flower. It was Feb. I may not have recognised M. tetrancistra back then, so will have to check my few colour slides.

Thanks, Chris. These hillsides of Ferocacti are amazing there, indeed. It takes some time to learn how to find small mammillarias among them.