After submitting an image of one of the galls to What’s that Bug? and learning that no one there knew what kind of gall it was (and they still don’t, as of today), I did a little searching on the internet and continued to come up fairly empty-handed. Last year’s galls were twig galls, or appeared to be so from the way they were attached to the tree.

Now there’s another type of gall on this tree – a leaf gall, which is a more common type of gall than a twig gall.

If you click on the image to enlarge it, you’ll see the leaf and how the growth appears to tuck into it. The leaf itself is producing this growth, of course, but it looks like the gall is just snuggling up to the leaf. You may be able to tell, also, that most of the leaves in this image are new – they’re a light green compared to the older leaves, which are dark green. Also, young flower buds can be seen here and there. This timing of the appearance of the galls brings home a statement from wikipedia on galls:

In order to form galls, the insects must seize the time when plant cell division occurs quickly: the growing season, usually spring in temperate climates, but which is extended in the tropics.

The insect naturally wants its home and food to grow rapidly, so here in Panama, anyway, this insect has chosen to settle on the splendid myrtle just as it’s putting out new leaves and flower buds.

Practically the only material I can find on galls and plants in the myrtle family is the observation that there are lots of them. In Australia, half the galls found have been on plants from the family Myrtaceae (Mo Bot Garden).

Worldwide, though, galls may be more likely to occur under certain ecological conditions than with specific plant associations. More species of galls are found in nutritionally poor habitats than in richer habitats. They are more likely to be found in association with woody plants that have leaves designed to conserve water than in association with plants without these characteristics (Fernandes et al., 2002). It happens that the splendid myrtle lives in nutrient poor abandoned pasturelands. It also happens that the shiny leaves of the splendid myrtle strike me – subjectively of course – as more likely to be water conservers than water wasters.

That’s about all I’ve been able to dig up. If anyone knows anything at all about galls here in Panama, or Central America, or the entire neotropics, please speak up.

Since my curiosity was peaked by the apparently rapid opening of the Davilla flower, I decided to watch the guava closely while waiting for a Davilla bud to decide to open.

Here’s what I saw this morning, between 6:54 AM and 8:05 AM. It took about an hour and a quarter for the flower to go from a bud to a fully open flower. (Click on any image to enlarge.)

And then, when I returned after 3 in the afternoon, here was the fully mature flower.

Now go back and look at all the images again, paying attention to the flower on the left of the blooming one. What happens to it is what is going to happen to today’s blooming flower tomorrow. First the petals wilt and the stamens begin falling away By mid-afternoon all the stamens are gone. Only the pistil (female part) remains and you can see the fruit beginning to develop beneath it.

Ain’t nature grand?

Technorati Tags: flowers, guava, petals, pistil, stamens

The first plant grows in very poor soil – even poorer than the average on our abandoned-pastureland/depleted-soil property. We have a few areas that are so rocky and the soil so thin that the only way it can be maintained is by weed-eater. On this particular slope we have let some shrubs survive the weed-eater in the hope that some day the area will develop into a natural site for native trees and shrubs.

Looking from the top of the slope down toward the gully where rainy season rain drains into the quebrada (seasonal spring) we can see several shrubs. I’ve circled a shrub of interest, coming closer to it in the next photo.

This shrub is in fruit now and although I failed to get a photograph when it was in flower last February, I have reason to believe it is a guayaba de sabana (guava of the savanna), Psidium guineense, which is in the Myrtaceae family.

The second plant grows in a relatively richer area. I did manage to get a photograph of one of its flowers, and you can see the white petals and many stamens of a typical myrtle family flower. The area has fewer rocks than the slope and can be easily mowed. At various other places on the property, we have similar shrubs, and all of them seem identical to this second plant. The plant on the slope seems different from the rest in ways that you’ll soon see.

What makes me think it’s a guava?
Almost as soon as I learned to recognize members of the myrtle (Myrtaceae) family, I knew that these plants were in that family. The flower above certainly fit. The vegetative characteristics, you may remember from other posts (on Eugenia and on Myrcia), are quite simple:

• simple, opposite leaves with smooth margins or edges – both plants have them (left=slope; right=meadow)

• punctations (translucent dots) on the leaves – the ones on the slope are harder to see in the images because the tiny hairs obscure the punctations, even after clicking to enlarge, but they’re there – the indentations at the end of the arrows on the meadow leaf are somewhat easier to detect, especially after clicking to enlarge (left=slope; right=meadow)

• thin, peeling bark (usually) – both plants have typical Myrtaceae bark (left=slope; right=meadow)

Determining the genus in this family, however, is not so simple. Gentry, who is so good at pointing out the simplest way to identify a family or genus, groups the various genera in Myrtaceae according to the features of the flower cluster, or inflorescence. Eugenia, for instance, is in a group where the

• inflorescence is a raceme (separate flowers attached by short equal stalks along a central stem)
• OR reduced to single flowers.

Psidium, by contrast, is in a group where the

• inflorescence usually has 3 to 15 or more flowers (with a shape different from a raceme botanically but that I don’t want to get bogged down by)
• OR may be reduced to single flowers on small stalks.

Gentry also points out the the leaves of Psidium have prominent secondary veins (the ones branching off the main vein running down the center of the leaf), a feature you can see on all the leaves in the images above. These features were not enough, though, to be certain of the genus. A Psidium specialist, Leslie R. Landrum, has stated that Psidium “…has long been one of the most difficult genera of American Myrtaceae to define. To do so, he uses a combination of floral and seed characters that I couldn’t possibly obtain in a short period of time.

So I turned to Carrasquilla, who has arranged the plants in his book, Trees and Shrubs of Panama, by family. He has only 5 plants listed in the family Myrtaceae, so it didn’t take long to recognize the genus – the guava genus called Psidium.

The Psidium genus

There are about 100 neotropical species of Psidium. They are all guavas and they are all evergreen trees or shrubs.

The name Psidium comes from the Greek word for pomegranate probably because guavas have lots of seeds, although guava seeds are certainly much smaller than pomegranate seeds, as you can see from the image of the ripe fruit at the beginning of this post and from this scan of the sliced green fruits from here.

Because most of the characteristics that distinguish Psidium from other genera in the Myrtaceae family have to do with fine details that I am not able to illustrate, I’ll jump right to the description of the species that Carrasquilla wrote about: Psidium guineense. The common name here in Panama is guayaba de sabana – the guava of the savanna – but it is also known as the Brazilian guava. The species name, guineense, was assigned by a botanist who believed that it originated from the Guinea Coast of Africa, but it did not. It is native to Latin America. It has been cultivated elsewhere, but you can see from this distribution map that its center is in the Neotropics. By clicking on the image you will see a few yellow dots in western Africa and northeastern Australia but all the rest of them are in Latin America.

Fruits of Warm Climates lists these characteristics, among others, for Psidium guineense:

• grayish leaves, 3.5-14 cm long and 2.5-8 cm wide
• leaves stiff, oblong, elliptic, ovate; scantily hairy on the upperside and coated beneath with rusty hairs
• flowers borne singly or in clusters of 3 in the leaf axils (where leaf meets stem) with 150-200 prominent stamens
• fruit round or pear-shaped from 1 to 2.5 cm

I highlighted the leaf characteristics because they 1) convinced me that the plant on the slope was P. guineense and 2) lead me on a bit of a goose-chase regarding the other plants on the property.

In the image below you can see that the undersides of the leaves (most of the leaves you’re seeing) have a rusty tinge. If you could feel them, you’d find them velvety with those rusty hairs. The leaves in the lower portion of the image are showing their upper sides and they do have that grayish tint to their green.

By contrast, the leaves of the plant in the meadow and of all other similar plants on the property are a greener color and have few hairs. If you were blindfolded and were handed a leaf from each plant, you’d have no trouble distinguishing the slope plant from the meadow plant.

Are there two species here?

For some time I was convinced that we had two guava species on the property. Not a single other plant on the property had the rusty-colored, velvety underside to the leaves that the slope plant has. Further, the leaves on the plant on the slope are smaller but the fruits larger than the leaves and fruits on the plant in the meadow. No other plant like this is on the property is in fruit, but the leaves of all the other plants have sizes like the plant in the meadow. I measured 10 leaves from each plant and got these averages:

slope leaves: 8 cm long x 4 cm wide
meadow leaves: 12 cm long x 7 cm wide

Fruits:

slope fruits: 3 cm long
meadow fruits: 1-2 cm long

I spent some time mulling over the differences, wondering whether they were meaningful, even reading up on the definition of species, which is disconcertingly vague. Then I remembered having read about the apple tree in Pollan’s The Botany of Desire: A Plant’s-Eye View of the World. The cultivated apple originated in the forests around Alma-Ata in Kazakhstan (Alma-Ata means “father of the apple,” says Pollan). A recent visitor to the area saw

“…entire forests of apples, three-hundred-year-old trees fifty feet tall and as big around as oaks, some of them bearing apples as large and red as modern cultivated varieties.”

So I thought, who knows how many species of apple were there in those forests? What’s important is that they were all apples.

And what we have here are guavas.

I did go so far as to track down descriptions of all six species of Psidium listed in the Flora of Panama Checklist, and I had to conclude that these plants are not different species. The main contender for the other species (which I really was rooting for) was Psidium guajava, the common guava. It, too, can have densely pubescent (hairy) undersides to the leaves. However, it has many more secondary veins (12-20 pairs) in its leaves than does P. guineense, which has about 8-10.

That clinched it. It seems to me that the number of veins in the leaves are much more likely to be characteristic of a species than the hairy-ness or the size. I content myself, then, with the guavas on our property, the guava of the savanna, Psidium guineense, while thinking of the apples in Kazakhstan, in all their variety.

Update: The online newspaper Hoy! from the Dominican Republic just published an article with recipes and health benefits of guava, an aspect of the fruit I completely failed to mention.

The unidentified tree in the gully, the one with the galls on it, belongs to this genus Myrcia. It was identified by a specialist in the Myrtaceae family at the Field Museum in Chicago, Lucia Kawasaki, and its full scientific name is Myrcia splendens. The potential waxy coat on the surface of this fruit is hinted at by its shine in the tree and perhaps even more so when seen close-up in a scan of fruits in various stages of ripeness:

However, Carrasquilla, the author of Trees and Shrubs of Panama, makes no mention of the use of the fruit for wax. He says the fruits are edible, sweet, and astringent. I think they’re sweet and spicy – maybe a little like allspice – but did not find them astringent. The bottom item in the scan, by the way, is the seed, not a small fruit. From that you can see that there’s not much pulp to the fruit. The seed is delicate and it’s easy to crunch right through it, thus destroying any pleasure from the sweetness of the fruit.

Carrasquilla, lists the distribution of the Myrcia splendens as being from Mexico to Peru and the West Indies, which corresponds to this distribution map from the Global Biodiversity Information Facility.

The species is listed at the US Department of Agriculture Plant Profile web site because of its presence in Puerto Rico and the Virgin Islands.

Just how splendid Myrcia splendens can get may be imagined from its listing in the Champion Trees of Puerto Rico where one such tree located in the Sabana Grande (the Grand Savanna) and last measured in 1966 was found to be

• 39.1 inches in circumference
• 41.0 ft in height and with a
• 25.5 ft crown spread.

I’ve measured only the circumference of the tree in the gully – it’s 19 inches around, so it’s a long way from challenging the champion.

One characteristic of the Myrtaceae family is a papery thin bark, epitomized (to me) by Eucalyptus bark (left image). So one of the reasons I was unsure of placing the gully tree into the Myrtaceae family was that its bark was coarse (right image). Once the Field Museum botanist identified the tree, though, and assured me that here was an exception to the guava-bark (guava being another myrtle and probably worth another post at some point) appearance, I put away my doubts.

To review

From the Eugenia post, plant may be a member if the Myrtaceae family if it has

• simple, opposite leaves with smooth margins
• punctations (translucent dots) on the leaves
• thin, peeling bark (usually)

To learn

A plant in the Myrtaceae family may be a member of the genus Myrcia if it has (Gentry)

• a well developed central axis to the inflorescence (flower cluster)
• usually has a set of young buds that look like stipules at the end of a twig
• may have hairs (trichomes) that look like Malpighiaceae hairs

Here are each of those traits on the gully tree:

The strong central axis.

Stipule-like buds at end of stem.

Malpighiaceae-like hairs. The Malpighiaceae family includes one of Panama’s favorite fruits – the nance. In these two images, the myrtle leaf is on the left (or top, depending on your browser) and the nance leaf is on the right (or bottom).

As for why this Myrcia is of the species splendens, this I have not been able to find out. The web site Trees, Shrubs and Palms of Panama lists 3 species of Myrcia (not splendens, however, although M. splendens is listed in the Flora of Panama Checklist as well as in Carrasquilla, of course).

One last tidbit on the Myrtaceae family pertains especially to our neotropical savanna/abandoned pastureland. Barwick, in the beautiful book Tropical & Subtropical Trees, says that the typical habitat for the slow-growing Myrtaceae is tropical American pastureland. Just for kicks, here’s the pasture just on the other side of the stone wall from our gully tree. No trees in that pasture, but our once-pasture was adjacent and nearly all of our trees spring up in abandoned pasture land. Myrcia splendens among them, I’ve just learned.

Last February, when several plants of the myrtle family (Myrtaceae) were in bloom with their small white flowers and many stamens, this tree, too, was in bloom with its small white flowers and many stamens.

Like the other representatives of the myrtle family, the leaves are simple and opposite, and with my hand lens I can persuade myself that the leaves have small translucent dots, called punctations, like all members of the myrtle family.

However, … I have yet to identify this tree and I’m not even 100% confident of those punctations. I recently saw some things in the tree, though, that may help, in the end, to identify it. These things are galls:

Galls provide both a home and food for developing insect larvae inside (one article about them was called To Have your House… and Eat it Too). Insects that cause plants to form galls are called gallers or gall-inducing insects. Many gallers are flies or wasps. Until recently, it was believed that there were about 13,000 species of gallers, mostly known from the northern hemisphere, but a survey published in 2007 estimated there may be ten times that amount – 133,000 species, with the estimates ranging from 21,000 to 211,000. There are some wonderful varieties of galls, several of which may be seen at What’s That Bug?

After the adult deposits an egg on the plant, the developing larva induces the plant to produce an abnormal growth. This growth becomes the larvae’s home and food supply. Unless a plant is infested with galls, the plant does not seem to be harmed by galls. Still, the plant does not derive any benefit from the gall and so gallers are considered parasites on the plants. Incidentally, not all galls are induced by insects – galls may be induced by bacteria, viruses, fungi, or nematode worms.

The reason the galls in these pictures may eventually help me identify my tree is that each galler tends to deposit its eggs on only one species of plant. So…if I were to identify the gall, I’d no doubt be able to identify the plant. Whether this has made my life easier or whether it has simply doubled my difficulties remains to be seen.

Update: The kind folks at What’s That Bug? have posted an image of my gall in the hopes that someone might recognize it. They did point out that this one is a twig gall, not a leaf gall, which is unusual. That’s a start.

The flower on the left has tannish anthers (pollen sacs) at the tips of the stamens and pink tinges at the base of the petals. If you click on the image to enlarge it, you should be able to see a greenish pistil (female reproductive part) near the middle of all the stamens.

The flower on the right has white anthers, all-white petals, and a white pistil.

Now for the berries:

The red berry on the left is the first fruit of the young cereza (Spanish for “cherry”) plant in our orchard, which we purchased from MIDA, the Panamanian government source for saplings and young plants. The green, maroon, and blue berries on the right are berries from the escobillo (Spanish for “broom” or, literally, “I sweep”) shrub growing on a volunteer, untended shrub in our yard. Below are the respective plants when they were in bloom.

Both these plants, the cultivated plant and the volunteer shrub, belong to the same genus of the family Myrtaceae. You might guess from the similarity of the flowers that they belong to the same family, but what makes them members of the Myrtaceae family in particular?

The Myrtaceae (Myrtle) Family

The family gets its name from the Myrtle genus, Myrtus, which is native to Europe and north Africa. A member of that genus, the common Myrtle, Myrtus communis, is said to have been sacred to Aphrodite and Demeter (wikipedia), but I haven’t been able to find out why.

Members of the myrtle family are woody with essential oils. They include: myrtle, clove, guava, feijoa, allspice, and eucalyptus (wikipedia). There are at least 3,000 species in the family and 130-150 genera.

To recognize a member of the Myrtaceae, Gentry (one of my favorite plant ID books for this area) says we need know only three characteristics of the leaves, at least for the Myrtaceae in our area.

The leaves are

• opposite
• simple
• pellucid-punctate (dotted with translucent pits)

Here are those characteristics in our two plants:

On the left is a stem from the plant in the orchard, showing simple leaves coming off opposite sides of the stem. On the right is a stem from the shrub, same thing. The shape of the leaves is quite different, but the arrangement of the leaves of each is opposite and the type of the leaves is simple (not compound – for more details on this distinction see here).

Those translucent pits can be seen pretty easily in the orchard plant. There’s a red rectangle in the left image (you can see it better by clicking on the image to enlarge it). The right image is a magnification the leaf section within that rectangle.

The pits in the leaves of the shrub are not so easily seen without magnification, so I scanned one for a better view. To have a comparison, I also scanned a leaf from the orchard plant. Again, the orchard plant is on the left, the shrub on the right. You can see the pits better in both cases in the enlargement.

So we have clear evidence that these plants belong to the Myrtaceae family – opposite, simple leaves with translucent pits.

The genus is harder to pinpoint. Gentry points out that although the family is very easy to recognize by the combination of the above characteristics, determining the genus is especially difficult in the Myrtaceae family. As frequently happens with me, I stumbled on the scientific name of one of these plants by accident, and the other followed as night by day. I was browsing through the wonderful book by Carrasquilla when I saw a picture of the broom plant…Eugenia biflora.

The Eugenia Genus

The genus was named by Linneaus himself – for Prince Eugene of Savoy (1663-1736), an Austrian general (Dave’s botanary) known for his patronage of the arts (Columbia Encyclopedia). Don’t ask me why Linneaus decided to honor the prince in this way!

Eugenia is found mostly in the New World. Like other members of the Myrtaceae, the sepals, which lie beneath the petals, stay on the plant after the petals fall off. Here are the sepals of the shrub, which I find quite attractive:

One of the distinguishing features of Eugenia species is that their flowers and fruits are carried on pedicels, or stalks. And here is where we come to the very close similarity of these two plants.

The scientific name of the plant from the orchard, the one with tannish anthers and pink tinges at the base of some of the petals, is Eugenia uniflora – which means single-flowered.

The scientific name of the plant from the yard, the all-white flower, is Eugenia biflora – which means with two flowers.

Here’s why (click on each image to enlarge):

The flower pedicel (arrow) for Eugenia uniflora, on the left, supports only one flower. The flower pedicel (arrow) for Eugenia biflora supports two flowers, more easily seen in the image after the petals have fallen away and only the sepals remain.

Very closely related, indeed!

The fruit of Eugenia uniflora is also known as the Suriname Cherry or the Brazilian Cherry. I missed getting a good picture of the fruit from our first-year plant, but A. V. Popovkin at Flickr has a great one, used here with his kind permission:

You can see that the fruit is 8-lobed, like a little pumpkin. It’s high in vitamin C and when very ripe has a sweet taste which can be resinous. Here in Panama it’s simply called cereza and it is prized for eating as is and for jams.

Because it is valued as a fruit and an ornamental plant, E. uniflora has been distributed to places in the world well beyond its native Brazil and the Neotropics, as shown in this map from the Global Biodiversity Information Facility (GBIF).

The fruit of E. biflora is edible, but I don’t know that many people here take advantage of it. It’s pretty small and has a big seed, and so may not be worth the effort.

This plant has not been distributed as widely as E. uniflora. It is confined to the West Indies and Central and South America.

Here in Panama, the leaves and branches are put to good use in some areas as brooms, and, as mentioned, the common name for the plant is escobillo, meaning “I sweep.” I remember a day in early January a couple of years ago while waiting for our weed-eater to be repaired visiting with the wife of the mechanic. She told me that it was a New Year’s custom to make a new broom for the house.

She promptly went out into her yard, cut some branches from from an escobillo shrub, lashed them to a pole, and handed me my New Year’s broom. It worked, too!