Chihuahuan ringstem is native to southwestern Texas (Big Bend area) and northeastern Chihuahua. It is a gypsophilic (gypsum-loving) species. Instead of duplicating efforts on explaining the relationship of plants and gypsum, I urge you to visit the photographer Gary Nored’s weblog aneyefortexas, where he writes expertly on the topic in this post: Gypsum, and the Plants that Live On It.
Ringstems are so named because of the glutinous brown bands occurring on the stem internodes (i.e., along the areas where the stem extends between leaves, buds, etc.). A discriminating eye can see examples of this in today’s photograph, or it is more obvious in this photo of Anulocaulis annulatus. To reinforce the notion of how uncommon this is in plants, Anulocaulis literally means “ring” (Anulo-) “stem” (-caulis).
As for the rest of the name: leiosolenus is broken down to leio– meaning “smooth” and –solenus meaning “pipe”, presumably also in reference to the stem. Lastly, lasi– means “shaggy” and –anthus means “flowered”, so this is the shaggy-flowered variety of the species. For a species that has only four geographical groupings within a relatively restricted distribution, four varieties may seem like a lot, but, as the author of the Flora of North America entry notes:
Anulocaulis leiosolenus occurs as isolated, islandlike populations that are homogeneous within but differ slightly between populations. The turbinate fruits with prominent ribs and equatorial flange ridge, and the long-tubular perianths, are unifying features.