Excerpts from Jim Conrad's
Naturalist Newsletter

from the August 7, 2016 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins, central Yucatán MÉXICO
SCHWENKIA

In the limestone quarry's very thin, hard-baked, deserty soil, stood a knee-high herbaceous plant I hadn't seen, this one at the end of its flowering period, with its upper branches contorted from drying out and dying back. Below, you can see what look like little more than the twisty remains of the plant:

SCHWENCKIA AMERICANA

This large, diffuse cluster of flowers, or inflorescence, arose from a base bearing only a few, small leaves, shown below:

SCHWENCKIA AMERICANA, leaves

The flowers were so small and slender that they were easy to overlook, but they could be found at some of the gnarly inflorescence branch-tips, as seen below:

SCHWENCKIA AMERICANA, flowers

Closer up, the corolla reveals itself as little more than a long, slender, purplish cylinder with very modest lobes for petals, and the fruit shows itself as a classic capsule containing several seeds, arising inside a classic calyx with five sepals, as shown below:

SCHWENCKIA AMERICANA, flower and fruit

Below, a broken-open flower displays two of five stamens above which rises a slightly longer stigma-tipped style:

SCHWENCKIA AMERICANA, longitudinal section of flower

As blunt fingernails made the above field-dissection, something unusual was noticed at the corolla's mouth. The details were so minute that I couldn't see what was going on until the image came onto the laptop screen, shown below:

SCHWENCKIA AMERICANA, glands between corolla lobes

What are those club-like things arising between the corolla lobes? Seeing this, I knew I had something special.

It took extra time to identify this plant because at first I couldn't figure out which plant family it belonged to. Because of its capsular fruits and its growing in such thin soil atop limestone, initially I thought it was a member of the Pink Family, the Caryophylaceae, along with the sandworts, genus Arenaria, we've seen up North. However, the Pink Family is mostly a temperate and cold-weather family poorly represented in the tropics, plus they are opposite-leafed while our plant seems to produce one leaf per node, and it wasn't either of the two Pink Family members listed for the Yucatan.

My next bet was that it was in the Figwort or Snapdragon Family, the Scrophulariaceae, in which I've seen capsular fruits just like this, but it wasn't any of the Yucatan's several "scroph" species, either. On the Phylogenetic Tree of Life the Nightshade or Tobacco Family, the Solanaceae, stands right next to the scrophs, so I went looking there, though I'd never seen anything in that family with flowers bearing such appendages between their corolla lobes. And, to my amazement, it turned out to be in that family.

It's SCHWENCKIA AMERICANA, though poorly documented on the Web, widely distributed in tropical America and, curiously, humid tropical Africa. It doesn't seem particularly adapted to thin, sun-baked soil atop limestone, but rather just flexible enough to be weedy in unexpected places like our limestone quarry.

For years taxonomists debated which family the genus Schwenckia belongs to. The great Linnaeus in the 1700s pegged it as a member of the Nightshade Family, but most influential botanists of the time placed it in the Figwort/Snapdragon Family, as I had done. As more information came in, the consensus grew that Linnaeus had been right with his Nightshade Family, the Solanaceae.

So, what are those club-like things arising between corolla lobes? I find one paper calling them glands, and I guess that that's right. The flowers look like they're pollinated by moths or butterflies with slender proboscises, but what good do such glands serve to a butterfly or moth? Maybe they attract pollinators such as small beetles and ants to the corolla's mouth, where they might be further enticed to enter the corolla tube to find fragrant nectar at the bottom, and do some pollinating on their way down? However they work, they're appropriately weird for a species that's so unique that it's the only representative of its genus.

In Africa, Schwenckia has been used in traditional medicine, and researchers have confirmed its anti-inflammatory properties.

Otherwise, not much seems to be known about it, so we're probably contributing valuable pictures and data here.