Peltastes, the Shield Liana

About this time last year, there was this flower on the ground.

When I looked straight up to see where it came from, all I could see were the leaves and green fruits of a nance tree. I looked down at the ground again, and I found another flower, with an upside-down leaf.

It took awhile before I stepped far enough away from the tree to see what was growing on top of the nance.

A liana, with peltate leaves.

Hard to see, though. Grabbed binoculars, then camera with zoom lens.

Okay. What about on the ground – were there any nearby so I can get a better look?

Well, there were some young plants with peltate leaves under that nance tree. No flowers.

Flowers, peltate leaf, liana. The flower looks so much like an Allamanda that I thought this liana must be in the same family. It seemed at the time that these features might be enough to go on.

Then, it being the rainy season with lots of work needed to keep the jungle from taking over, I let it drop. Until the flowers started appearing again this year, and I decided to get serious about it. Never mind the encroaching jungle.

First I checked with both Gentry and Elpel for a quick list of characteristics that would define the family.

Characteristics of the Family Apocynaceae

• Profuse latex – well, yes. I’m used to white latex in this family, but this time it’s clear, and I couldn’t get a convincing picture of it, but I could see it and feel it. A bit sticky. Moderately thick.
• Opposite, simple leaves, no teeth on the margins.
• 
• Tubular flowers with parts (sepals and petals) in fives. Here are the petals on the left and the best I could do with the sepals on the right.
• 
• Fruit a berry or follicle, often in pairs. The next image is of the follicle, which showed up about four months later. The one outlined against the sky is distinctive, but notice many more to the right. (Botanical asides: Follicle: a dry fruit that is derived from a single carpel and opens on one side only to release its seeds. In the case of this plant, the seeds are wind-borne. Carpel: the female reproductive organ of a flower, consisting of an ovary, a stigma, and usually a style. It may occur singly or as one of a group.)

Okay. I think that’s enough to put it in the Apocynaceae, or Dogbane, Family.

Finding the Genus

Gentry breaks this family down into four main groups: two groups of trees and two of vines or lianas.

The two liana groups are separated depending on whether they have (group 1) small flowers or glands on the midvein, or (group 2) large flowers and no glands on the leaves.

This liana has no glands on its midveins.

Gentry finds three distinctive genera in this group: Allamanda (“Our only climbing apoc with whorled leaves.”), Anechites (“Slender vine with very characteristic hooked hairs on stem and inflorescence causing plant to stick like bedstraw.”), and Peltastes (“Unique in peltate leaf.”

That peltate leaf. Gives the genus, Peltastes, its name.

There are 7 species of the genus in South America, but only one species is found in Central America, Peltastes isthmicus. R. E. Woodson, Jr. named the genus in 1932 and, in an overview of the Family Apocynaceae published in 1936, gave the following description to Peltastes isthmicus:

• Stems ferruginous-lanulose when young [Note the reddish-brown, wooly appearance in the image illustrating opposite leaves.]
• Leaves long-petiolate, broadly ovate, 10-30 cm long, abruptly short-acuminate, broadly rounded at the base, elaborate above, ferruginous-lanulose beneath when young [Long petioles or leaf stems; broad oval shape; dimensions about right; short, sharp tip]
• Calyx lobes oblong-ovate [See the image of sepals, above. A calyx is a collection of sepals. ]
• Corolla glabrous outside, the tube 2.5 cm long, the throat 2 cm long, the lobes 3.5 cm long [Petals smooth outside. Dimensions about right.]
• Follicles 22-25 cm long [Dimensions about right.]

I think that’s it.

From Wikimedia

I’ve always liked peltate leaves, with that leaf stem inserted in the middle, roughly, of the leaf itself. But until I looked into this plant, I never realized where the term “peltate” comes from. It’s from pelta, a small shield used by the  Tracians.

Further, peltastes was a soldier armed with a pelta. (Plural for peltastes is peltastae.)
And there we have that shield, up in the canopy, protecting, it looks like, the inflorescences.

Briefly, How to Recognize

As a member of the Apocynaceae Family, this liana has:

• clear latex
• simple, opposite leaves, with toothless edges
• tubular flowers
• fruit as a paired follicle

The genus, Peltastes, is recognized by its

• peltate leaves

The species, P. isthmiticus, is the only species of the genus in Central America.

Related articles

• A Tree Hugger, With a Twist (nytimes.com)