The Leaf inside the Flower

This vine belongs to the plant family Malpighiaceae, which is the family of the nance, a favorite fruit tree here in Panama. Because the family is represented only in the tropics and subtropics, I want to spend a little time comparing the parts of the nance plant with this vine, thereby looking closely at some of the family’s characteristics.

First, though, about that awkward family name – Malpighiaceae. I’ve heard botanists shorten it to something that sounds like “Malpiggy,” which I suppose is correct enough for pronunciation, but which sounds, in English, unjust to the Italian scientist for whom the family was named: Marcello Malpighi, a 17th century anatomist. We humans have a Malpighi skin layer, and we have Malpighian corpuscles in our kidneys and spleen. So why is a plant family named for him? Because he also looked at “plant anatomy” under the microscope and wrote a book about what he saw – the Anatomia Plantarum.

One plant feature he must have described in some detail are plant hairs that are attached to a plant by the middle of the hair, not at either end. There’s a sketch at Plant Families of the Dominican Republic, a site, by the way, that has an excellent description of the Malpighiaceae family.

The sketch shows the characteristic clawed petals of the flower on the left, the Malpighian Hairs at the top right, and the winged fruit, like the maple wing, at the lower right. It’s worth taking a closer look at the vine flower and the nance flower to see these details.

Malpighi flowers have claws

Here’s a closer look at the vine flower,

compared with nance flower.

Look at the bumps between the claws of the petals – they’re green in the vine flower and yellow in the nance flower. These are oil glands. Many flowers in the Malpighiaceae family are pollinated by bees that collect oil from the flower while pollinating it.

The flowers occur in clusters, although the clusters differ between the vine (at the left, below) and the nance tree (right, below).

Malpighi fruits are variable

We could not use the fruits of these plants to place them in any particular family. The fruit of the vine is a winged “samara,” which is the fruit of elms and maples (the vine samara, which occurs in 3s, is shown in the two images on the left, below). The nance fruit is a fleshy fruit formed from a single flower, a drupe, with one seed inside (the image on the right – the nance fruits are the ones in the bottle).

Malpighi leaves are simple and opposite.

Leaves may be simple or compound. Malpighi leaves are simple, consisting of one blade; each leaf bud produces only one blade.

Leaves also may be opposite, alternate, whorled, or spiral. If opposite, the blades are exactly opposite each other on the stem. Malpighi leaves are opposite, as you can see here. The vine leaves are on the left, the nance leaves on the right.

 

Malpighi plants may be lianas or trees

Lianas are woody vines that start at ground level and climb trees to reach as much light as possible. They are common in rainforests, but also are found in temperate zones. Clematis, for example, is a liana (wikipedia). Today’s plant is growing on the ground in a disturbed area and has started climbing nearby shrubs. Nance is a tree. The vine, or liana, is on the left, the nance tree on the right.

Malpighi plants may have stipules

Linneaus himself, “Father of Taxonomy,” came up with the term stipule. A stipule is an outgrowth on either side of the base of the leaf stalk. In today’s plant, the stipules are small, scale-like, and triangular. You’ll need to click on the image at the left to enlarge it enough to see the stipules. Zero in at the point where the leaf stalks meet the stem. The nance stipules, by contrast, are relatively easy to see although you’ll probably want to enlarge the image on the right to see them better.

Finally, Malpighi plants have Malpighian hairs

You may have noticed the reddish hairs on the nance stem and leaf stalk in the image above, but it may not have been easy to see the hairs on the vine plant. Here’s a larger version of the underside of the leaf, but even so you may want to enlarge it to see the hairs well. While you’re looking, you may notice the swelling of the leaf stalk just at the base of the leaf blade. Those are leaf glands, and are common in the Malpighiaceae family.

To summarize the Malpighiaceae family characteristics that this vine and the nance share, then are:

• Flowers with clawed petals
• Simple, opposite leaves
• Stipules
• Malpighian hairs

We also looked at their fruits, which are not a family characteristic, and we saw that one is a vine, the other a tree.

Now to classify, as far as possible, the vine itself.

I used Gentry‘s field guide/key to the woody plants of Northwest South America to get a handle on the species. Gentry divides the Malpighiaceae family (about 60 genera) into two large groups:

1. Trees and shrubs with unwinged fruits [the nance tree (genus Byrsonima) goes here]
2. Lianas with wind or water-dispersed fruits [today's vine plant goes here]

He then breaks down each group into smaller groups. The small group into which this vine falls is the group with maple-like wings. He puts four common genera into this group. I’ll only discuss the one that seem most feasible to me: Stigmaphyllon.

Genus name

It’s because of Stigmaphyllon that this post has the title it does. The name Stigmaphyllon comes from “stigma,” which is the part of the female structure that receives pollen during pollination, and “-phyllon” which means “leaf.” According to Arthur Gibson, Garden Director for the UCLA Botanical Garden, … each stigma bears a very conspicuous leafy portion next to the sticky stigmatic tip. Once I started looking for the three leaves, I found them. Here’s a close-up of the center portion of the flower:

You can easily see those leafy structures at the right. On the left you see the green oil glands of the sepals.

Gentry states that the leaves of Stigmaphyllon usually have a heart-shaped base and those that don’t have such leaves do have unusually large glands on the leaf stem. These descriptions make me a little uneasy, because the leaves on this vine are elliptical, without a heart-shaped base. Further, I don’t have enough experience to know whether the glands on the leaf stem are unusually large. Nevertheless, Stigmaphyllon is the best fit I have for a genus.

Species name

As far as species… Discover Life lists 18 species in the genus Stigmaphyllon (do a search for Stigmaphyllon to see the list). Only 4 species have illustrations, but one of them is S. ellipticum, which seems awfully similar to this plant, and nearly satisfies my concern about leaf shape. Certainly the species name is encouraging!

Having been stung on species identification before, however, I’m assigning this plant an extremely tenuous identification: Stigmaphyllon (probable genus) ellipticum (possible species). The proper botanical name would be Stigmaphyllon ellipticum (Humb., Bonpl. & Kunth) A. Juss. In the meantime, I’ve saved a sample in my plant press and hope to get a real identification one of these days.