A Neotropical Savanna

The nance trees on our property have been in bloom for a couple of months, although they are just now really ablaze with color. All this time I’ve been trying to get a decent picture of an individual flower. This is not it – these are the flower clusters (inflorescences) on the tree.

The nance, Byrsonima crassifolia, is one of the three conspicuous trees in this savanna. It’s often a host for orchids,

and its fruit is used to make juice and to flavor ice cream. Different parts of the plant are used throughout the American tropics for medicinal purposes such as treating snake bites, diarrhea and dysentery, bad coughs, and reducing fever.

I’ve worked through the taxonomy of nance, before, showing that it is in the family Malpighiaceae. But what features of this plant put it in that family, relating it to acerola and about 1300 other species, most of whom are native to the new world?

For on thing they often have reddish hairs.

Not only do we see in this image the reddish hairs, but we see three other characteristics of Malpighiaceae:

1. simple (not compound) leaves
2. opposite (rather than alternate) leaves
3. stipules

The stipules are those small appendages at the base of the leaf stalk. If you read about the stipules that characterize the coffee family (Rubiaceae), you may remember that those were interpetiolar stipules – ones that occur between the bases of the petioles. The stipules of the Malpighiaceae may be either interpetiolar or intrapetiolar stipules – ones that occur at the base of the petioles. Here in Byrsonima, the stipules are intrapetiolar – at the base of the petiole.

The flowers, though, are most distinctive. They occur in clusters either at the ends of stalks or branches (terminal) or at the angle between the leaf stalk and stem (axillary). Nance inflorescences are terminal. The young flowers are yellow and as they age, they turn orange in color.

Each flower within the cluster has

1. three carpels (female organs)
2. “several” fertile stamens (male organs)
3. five petals with clawed bases, commonly fringed or toothed.

Most interesting to me are those clawed, fringed petals. That’s what I’ve been trying to get a picture of. I’ve scanned, taken macros indoors and out, and have had abominable results.

You can get an idea, I think, with this one:

You can certainly see the 5 clawed, fringed petals. The carpels and stamens are there in the center, but you could not prove it by me which are the three carpels and which of the remainder are the stamens.

Byrsonima flowers produce lipids instead of nectar. In the next image you can see the glands that produce this oil. They are located over the sepals. (You can also see those reddish “malpighian” hairs on the flower stalk.)

Bees of the genus Centris obtain both pollen and oil at each visit to the flower. The mixture of oil and pollen is fed to bee larvae. Adult bees feed themselves with nectar from other species of plants.

I’ve gone a little beyond the family characteristics here, once I zeroed in on the flower. So let me just summarize what I now know to look for to recognize the Malpighiaceae family.

1. reddish hairs
2. simple, opposite leaves
3. stipules
4. flowers with 5 clawed, fringed petals

These should suffice in the field to at least tell me the plant is likely to be a member of the family.

Now what sets the nance tree apart from the other members of the family? I found an excellent description of Byrsonima crassifolia written by Mireya D. Correa A. at the University of Panama and Smithsonian Tropical Research Institute. My botanical skills are still too naive to pluck the key species features from the description, but much in that document is of interest. All the information in the next two paragraphs is gleaned from that paper.

The nance tree is resistant to fire and therefore has a mode of growth that makes it appear twisted. [I wonder, but haven't been able to find out, whether this twistedness creates nice little niches for the orchids. I also see more epiphytes on the nance than on other trees in the relatively dry climate of a savanna. Hmm.] It is found in both wet and dry tropical forests but usually grows in barren soils at elevations up to 1500 m. The bark is fissured, gray to dark chocolate color, with lenticels.

It flowers from November through July, primarily from March through June, for approximately 6 weeks. One fruit (drupe) is produced from each flower. They ripen primarily in August and September and are dispersed by birds. Humans harvest the fruits by collecting them from the ground, by hand. Fruits can be made to fall from branches by shaking them or, if the branches are not accessible, by throwing a piece of wood and hitting the branches. The fruits are tightly stuffed into previously cleaned bottles with water and are sold this way.

All this discussion is creating a craving for nance ice cream. I’ve heard it described as tasting walnut-flavored, but I don’t taste it that way. Nance does add a richness to the taste, though. Now I’m going to have to wait until August when nance ice cream will reappear in the stores!