John and I today botanized Maggy’s Hammock near Pt. Salerno, Fl, one of the nicer and botanically rich hammock remnants we know in Martin County, complete with massive oaks, handsome hickories, lancewoods, and graytwig bearing fancy stinkbugs. In flower was one of my all-time favorite plants, White Indigo Berry, Randia aculeata. (Aculeata means thorny.) This gnarly, spiny slowpoke ranges from Florida through the Caribbean to South America. It is poorly studied, which is a pity, because this idiosyncratic shrub clearly harbors secrets. We’ll guess at some.
A member of the Coffee Family, it is related to Gardenia, and thus has fragrant flowers looking like those on coffee itself. Even smellier, the related Randia ruizana a perfume plant, called Angel of the Night. Bees, butterflies, and who knows what else visit our species, perhaps moths?
As a good member of the Coffee Family, Randias are little green Big Pharmas. Every plant you encounter has some history in medicine somewhere, or some positive medically compelling screening result, but species of Randia have more historical and present-day points of medicinal interest than you can shake a stick at, serving for everything from parasitic worms to easing pain, an attribute well known in other members of the family. In Mexico White Indigo Berry is traditionally the Rx for venomous serpents. Just what the doctor ordered when the doctor is a snakebite specialist known as a culebrero. (Culebra = snake.) Silly legend? Now hold on, before that derisive snort consider a study by the National Polytechnic Institute in Mexico City illuminating multifaceted ways Randia aculeata extract protects mouse tissue from toxic venom.
The fruit has a specialized structure. When ripe it is about the size of a marble and white or creamy on the outside. Inside, though, the seeds are plastered in a dark blue pulp. The blue goo gives blue dyes for skin and fabric, including calico.
I guess the pulp might be more or less edible (?) although not attractive, although the many bioactive contents worry me. Randia eaters might prefer Randia formosa (Rosenbergiodendron formosum) known as Blackberry Jam Fruit, which offers more-luciousness.
General experience around White Indigo Berry shows a lot of the fruits not to wind up as bird food, although many perhaps do too. I think we have a case of an originally fleshy birdfood fruit evolving into a bobber riding the ocean waves. Did I mention that Randia aculeata favors maritime habitats? The dark inner pulp shrinks, coating the seeds and creating air space.
That flesh is called “pulpa.” It is not ordinary fruit flesh, but instead comes from the innermost fruit layer in intimate contact with the seeds. I bet this material contains germination inhibitors to keep the seeds safely asleep while afloat, like Astronauts in suspended animation for 1000 years en route to a distant galaxy.
To descend deeper into shameless speculation, species of Randia, like many plants, make mannitol. In the plant world as well as in the hospital, mannitol can help restore or alter electrolyte balance, which is why it works as a laxative, drawing water osmotically into the intestine. A fruit floating in the salty sea may need to draw in water osmotically too, given its bath in the water-sucking salty sea. Mannitol in the pulp might help, and/or it may retain precious water elsewhere in the plant coping with a dry sandy salty habitat. Mannitol or not, that tar covering the seeds obviously protects them physically, and the toxic ingredients probably suppress stowaway bacteria and fungi during the voyage.