A Neotropical Savanna

Agro of Midora has been doing some interesting hands-on work as he learns plant identification. He did a great job working through the identification of an Ixora plant in his front yard. It’s really worth your while to go look at the post if for no other reason than to enjoy his sketches of the plant.

He did run into some questions about plant parts and, undeterred, has done a follow-up study on the sepals of Ixora. The petals of the Ixora flower are long and slender and appear to arise directly from the pedicel, or flower stalk. By way of review, a typical flower consists of a series of whorls starting on the outside with a whorl of sepals (the whorl is called a “calyx”), then a whorl of petals (called a “corolla”), a whorl of pollen-bearing stamens, and finally an inner pistil that leads to the ovary. (Image from Wikimedia Commons).

Few flowers look just like the model, though, and in the case of Ixora, that outer whorl of sepals is hard to see. In the model flower, sepals look like small leaves or maybe like small green petals. In Ixora they’re very different.

Intrigued by Agro’s work, I went out and clipped a flower from one of our bushes and looked for the sepals. I couldn’t see them very well until I scanned them at a fairly high resolution, which allowed me to magnify the view and look at the details.

Here’s a portion of an inflorescence. We’re going to be looking at the knobs at the base of the petals.

I ruthlessly pulled off the petals, taking the stamens with them – the stamens in Ixora adhere to the petals. This action left a clear view of the pistil (with the stigma and style showing) emerging from the calyx, which is, of course, the whorl of sepals.

Notice, first, that the calyx is not green as in the model flower.

Notice next that the sepals are not leaf-like or petal-like individual structures.

Having learned previously that Ixora should have 4 sepals, I went to another description of the genus and found that the sepals in Ixora form a calyx cup with 4 to 5 lobes [Dwyer]. The segment just below the calyx cup is the pedicel, and the calyx cup itself looks a bit like another pedicel.

No wonder Ixora sepals are hard to see – they’ve made themselves into a cup rather than looking like little green petals!

If you now compare these images with Agro’s, you’ll see the sepals definitely come from a plant of the same genus. But because there are more that 400 species of Ixora [Dwyer], it is up to each of us to learn which species we have (maybe Agro already knows his – I don’t know mine, though).

But that’s for another day.

Technorati Tags: calyx, petals, corolla, sepals, stigma, style

Many years ago when I lived in New York City, I went birding with a small group of Audubon pros. I’ll never forget the time when one woman said, pointing to a bird whose name I’ve forgotten,

There it is – on the verbena bush!

We were in Central Park and there were lots of bushes around – and I had never heard of a verbena bush and I certainly would not have been able to recognize one. (I think I did find the bird, though.) At any rate, whenever I think about the Verbenaceae (or verbena) family these days, that incident always comes to mind, and my memory searches through those sunlit bushes, trying to guess which one is the verbena.

The memory is particularly amusing because, according to wikipedia, most plants in this family are tropical – not your basic NYC habitat. Nevertheless, the family is widespread, as we’ll see later. Here in Panama, the lantana (Lantana camara) that grows wild around our yard belongs to the Verbenaceae, as does Michael’s sandpaper vine, Petrea volubilis, and even the teak tree (Tectona grandis).

As does this plant that I’ve seen growing along roadsides, in an opening in the depth of a pine forest, and in the gardens of many of my neighbors.

It’s commonly called porterweed – Stachytarpheta mutabilis (Jacq.) Vahl.

So what do all these plants, including a tree, have in common, that they should be grouped in the same family?

Read more »

The latest carnival of plant blogs from Berry Go Round is up at Not Exactly Rocket Science. Lots of interesting links, including pointers to surreal plants (that exist in imagination only), a Google Earth tool for naturalists, and plenty of gorgeous photos. The link is here.