Diario de ellen5

We've had a number of interesting cymopterus observations up our way, lately. But we're having trouble finding a trustworthy source for identifying these at the species level. It seems the most authoritative sources are in disagreement with one another.
Does anyone have a recommendation as to a really good treatment on distinguishing these?

Unidentifiable observations may have the most value.

OK, so you've found an unusual plant. Let's say it might be a milkweed, one you've never seen before.
Do you pick a leaf to check out the latex?
Did you just damage that plant?And is this a rare species of milkweed?
Is your curiousity more important than the survival of that species, and all other interrelated species in its habitat?
Take a photo, and LEAVE THINGS ALONE

If anything can drive me away from iNaturalist, it's going to be people arguing about taxonomy.