Echinocereus viridiflorus seedlings     2/23/20
And one more set of seedlings from that same sowing date. I toss this in to point out that probably more than 50% of all cactus seedlings at this age look alike. That is, if I didn't tell you that these are Echinocereus seedlings, you, or maybe even a cactus pro, wouldn't know the species - or the genus, even, in many cases. As I do more and more seeds, I'm getting to have better educated guesses about genera. Species are still a hard guess. I bet my friend Steven Brack could make good guesses about species, but this was his profession for about 40 years. I was just an organic chemist all the years he was looking at cacti.
The preceding picture is noteworthy in that looking at the seedlings, all you can say is - different from most cactus seedlings. I don't think Echinofossulocactus would spring up in my mind, having never seen them. But now that I've seen these for so long (4 weeks!!), looking at them and counting them over the germination period, I might file away the appearance and yell "Echinofossulocactus sulphureus" the next time I see a bunch as those illustrated. Of course, my chances of being selected for "Jeopardy!" on TV are vanishingly small. (24/24)