Cissus the Scrambler

In this rainiest of La Niña rainy seasons, everything in the pine forest where I walk the dogs is green, green, green. A spot of red, then, really catches the eye, even when it’s against the clay dirt of a forestry road.

There are lots of sprawling, scrambling vines around, but this one I like because of its red inflorescence and also its trifoliate leaves. When I took a clipping or two home and and opened my trusted identification manual by Gentry in hand, it didn’t take long to come up with the family and genus name of this woody vine.

Leaves alternate and compound

The leaves are divided into three leaflets, which makes them compound leaves, and they are not opposite each other on the stem – they work their way up the stem on alternate sides.

This combination of alternate, compound leaves is most often found in the legume (Fabaceae) family, but legume leaves have smooth edges or margins. The margins of the leaves on this woody vine are toothed, or serrated.

The toothed edges place it in one of three possible families: the soapberry (Sapindaceae), the cucumber (Cucurbitaceae), or the grape (Vitaceae) family.

Crucial tendrils

To distinguish the families from each other, Gentry uses the configuration of the tendrils. Soapberry tendrils are bifurcated or forked. Cucumber tendrils are divided, spirally coiling, and make a right angle with the base of the leaf stalk. Grape tendrils arise on the stem opposite the leaf stalk – in the exact position another leaf would be if these leaves were opposite rather than alternate.

So which tendrils do we have here?

Member of the Vitaceae family

The tendril arises on the stem opposite the leaf stalk, which makes it a member of the grape, or Vitaceae, family.

Member of the Cissus genus

Once the plant had been placed in the grape family, it was straightforward to find the genus. In the discussion of Vitaceae, Gentry says:

Several Cissus species have 3-foliate leaves. The commonest of these have a characteristic 4-angled, subwinged branchlet . . . also usually distinctive in swollen nodes.

Here’s the 4-angled stem:

Nodes are where the leaves are attached to the stem. You can get a hint of the swollen node in the above picture. It’s a little more dramatic in this one:

Botanical Aside: Why I love Gentry

To me, those three easy-to-see characteristics listed by Gentry took me straight to the genus name of this plant. Had I not used this book and had somehow managed to place the plant in the Vitaceae family, I would have then turned to the classic paper on Vitaceae by Elias, in the Flora of Panama series.

There I would have learned that the grape family is represented by only two genera in Panama – Vitis and Cissus – and these two are distinguished, by their flower clusters, or inflorescences.

Vitis has paniculate flower clusters. Cissus has cymose flower clusters. Vitis is the genus name for grapes, including the cultivated grape, Vitis vinifera. Its inflorescence is on the left (photo from wikimedia commons) and the inflorescence for my Cissus vine is on the right. A panicle (adjective = paniculate) on the left and a cyme (adjective = cymose) on the right. Can you tell the difference just by looking?

I can’t. Inflorescence terminology is something that intimidates me greatly, and if the terms in the last paragraph had your head spinning, I sympathize. I find myself learning the terms on a need-to-know basis. I decided I needed to know the difference between paniculate and cymose in this case so I looked up the terms.

It got a little more complicated when I found that the grape panicles are racemose and that the Cissus cymes are compound. In the end, the important part about distinguishing these flower clusters is discovering the order in which the flowers mature.

• • In a cyme, the flower at the end of the stem matures first.
  • In the grape panicle, the flower at the base of the central stem of the flower cluster matures first. The fact that the panicle is racemose is what tells you this.

These are important differences, but for an amateur who wants to get to the name first and to study the botany and ecology with name in hand, it slows one down to use inflorescence as a distinguishing characteristic. If the leaf type and arrangement can do it, then I’m all for it.

So that’s why I love Gentry. I learned that the plant in my hand was a Cissus without having to first learn the difference between cyme and raceme. But, of course, now that I do know the difference, I can do something with it, and so here we go.

Proof of cyme, anyway: In a simple cyme, the flower at the end of the stem matures first. In a compound cyme the flower at the end of each axil in the flower cluster matures first. So here’s a look at an individual axil. Sure enough, the central, terminal flower has clearly matured before the other flowers on the axil; the fruit has already developed from the central flower (and it is in focus whereas the flowers elsewhere are not).

So this woody vine is in the genus Cissus, by all kinds of criteria.

Incidentally, a very nice sequence of racemose flower maturation (shown in grapes, not in Cissus) is in this post on Virginia Sweetspire. It may help to know that the word raceme comes from the Latin racemus, which means “bunch of grapes.”

End of Botanical Aside: Enough on cyme, cymose, panicle, and racemose, then.

Working out the species

When Elias worked out the key for Panamanian Cissus, he listed four species that were trifoliate. For now, let’s call them species A, B, C, and D.

To sort them out, first characteristic he looked at was whether the leaves were rhombic in shape or elliptical to oval, with the narrower end at the base. He made note that the plants with rhombic-shaped leaves tended to be fuzzy with hairs. The leaflets in this Cissus (seen in the image earlier) are more or less oval shaped and are smooth to the touch. The Cissus with rhombic-shaped leaves is species A.

Then the species with leaves that are roughly oval and smooth to the touch are separated on the basis of the length of the peduncle, or the main stalk of the flower cluster. If it’s between 7 and 12 cm long, its stems tend to be 4-sided and the fruits 4-6 mm in diameter. This is Cissus species B.

Here we see a stalk that 7.4 cm long and a nearly mature fruit that is 5 mm in diameter.

If the stalk is shorter and the fruits larger, then we have species C or D and they are further distinguished by other criteria..

So by the criteria of flower stalk size and fruit size, together with the 4-sided stem, this woody vine, species B, is Cissus erosa.

PS: The names of all four species of Cissus described by Elias in 1968 are:

• species A = C. rhombifolia
• species B = C. erosa
• species C = C. microcarpa
• species D = C. martiniana

We now know that there are more species of Cissus in Panama than these four, but that’s enough for now.

Cissus erosa

Cissus is the Latin name for ivy. (Certain cultivated species of Cissus are called “grape ivy.”) In the United States, plants of the genus Cissus are called “treebine,” and these plants are often compared to Virginia Creeper or five-leaved ivy. Same family, different genus.

The species name erosa means jagged, perhaps because of the rather rough leaf stalk. Here’s a zoom in on the stem image:

Cissus erosa is widely distributed in Central and South America, where it is known as caro de tres hojas or “dear three leaves.”

Why Scrambler?

The title of this post is “Cissus the Scrambler.” The thought of a vine or liana as “scrambling” over low-lying plants or, in the case of some of these plants, over a forestry road, came to me after reading a chapter about “Hangers On” in the book Tropical Nature. There’s a great discussion of the impact a climbing vine can have on the tree that it is climbing. It can, in fact, be devastating.

All leaves, whether on a vine, a shrub, a tree or any other plant, need sunlight. If plants are near the ground, then they must either find a sunny area or adapt to the lesser sunlight in the shade of a tree. Woody vines or lianas, not having trunks or sturdy stems like shrubs, travel to reach the sun. They may use tendrils or they may use their entire stems to wrap around a shrub or tree and therefore climb.

A tendril can coil around small things – the tendrils of this Cissus erosa even coiled around pine needles and grass stems on the forest floor. These tendrils could never coil around a tree trunk, so lianas like this one sprawl out in sunlit clearings, and may climb over small shrubs if their tendrils can wrap around the twigs. These are the scramblers, spreading out as fully as possible in forest clearings.

The lianas that climb trees must start out in the shade. They find their sun at the very top of the tree canopy, and the story of how they change as they climb by coiling their stem around the tree is a fascinating one, not to be discussed here (but read the book, it’s good!). There they start competing for space in the sun with the very trees they’ve climbed. No tendrils involved, but stems strong and sometimes thick enough to support large mammals.

Cissus, the scrambler, will never provide a swing for Tarzan. It finds the sun it needs close to the ground, in forest clearings, or crossing forestry roads.

Wrapping it up

Cissus erosa has

• alternate, compound (trifoliate) leaves
• tendrils opposite the leaf

which make it a member of the grape family, Vitaceae.

It has

• a 4-sided stem
• swollen nodes
• compound cymose inflorescence

which make it a member of the genus Cissus.

It has

• leaflets that are roughly oval and smooth to the touch
• a peduncle between 7 and 12 cm
• fruits 4-6 cm in diameter

which make it a member of the species erosa.

Its tendrils are fine enough to wrap around a pine needle or a grass stalk and are used to move the plant along across a clearing or to scramble over shrubs with thin twigs. Nowadays, when nearly everything in the forest is so very green, it’s nice to come upon a clearing and to see a cluster of red . . . a cyme (!) of Cissus.

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Note: The “Botanical Aside” was inspired by the “Side Notes” used in Watching the World Wake Up, where they are an art form.