Excerpts from Jim Conrad's
Naturalist Newsletter

from the June 18, 2017 Newsletter issued from Rancho Regensis north of Valladolid, Yucatán, MÉXICO
Last year as soon as I moved to the rancho, beside the entrance gate a certain tree caught my eye because of its eucalyptus-like trunk -- mottled gray and brown -- and fluted like a muscular arm, as shown below:

Psidium sartorianum, trunk

I couldn't identify it, so I've been waiting for it to flower. This week one morning at dawn during my pre-jog stretching next to the gate the loud buzzing of many nectar-gathering bees above me announced that the mystery tree at least was abloom. Below, you can see its glossy leaves and white flowers:

Psidium sartorianum, leaves and flowerss

At first glance I thought the white, puffball-like affairs were clusters of many tiny white flowers with their stamens extended, like those of acacia trees, of the Bean Family, but up close it was clear that each white item was is a single blossom with many stamens. Below, you can see this in a side viewa blossom from the side, showing stamens spreading in all directions from where the scoop-shaped petals' bases unite:

Psidium sartorianum, flower from side

The many stamens arise from a "disk" at the base of a slender, white, fingerlike, stigma-tipped style. Below, that's the style pointing toward the picture's top, right corner:

Psidium sartorianum, flower from from showing disk

Some of the tree's branches bore old flowers from which the stamens and petals had fallen, or were about to fall, but with the styles still attached, as shown below:

Psidium sartorianum, older flower

That image clearly shows that the flowers have "inferior ovaries" -- ovaries from the tops of which the petals and stamens emerge. Flowers in most plant families produce superior ovaries, so these inferior ones help a lot in figuring out the tree's identity.

The trees leaves were opposite one another on the twigs, and that's another good field mark, since most leaves alternate with one another. Below, you can see the green bases of two leaf petioles, with buds in the angle formed between the petioles and the stem:

Psidium sartorianum, stem node with buds

In the American tropics, when you have a woody plant bearing flowers with inferior ovaries and opposite leaves, the first plant family coming to mind is the big Coffee or Madder Family, the Rubiaceae. To confirm that you have a "Rube," you check to see that stipules arise on the twigs between the opposite leaf petioles. When the "interfoliar stipules" were sought on this tree, as seen in the above photo, they were NOT present, so our mystery tree was not a member of the Coffee Family. Besides, Coffee Family flower don't bear more than five stamens, so it couldn't have been that family, anyway.

Continuing "doing the botany," I recalled that the trunk was similar to that of a Eucalyptus. Eucalyptus belongs to the Myrtle Family, the Myrtaceae, plus flowers in the Myrtle Family produce many stamens atop each inferior ovary, just like our flowers. Remembering that not only menthol-smelling Eucalyptus belongs to the Myrtle Family but also the Allspice Tree and the fragrant Myrtle of the Mediterranean region, I crushed our mystery tree's leaves and was delighted with the resulting sweet-spicy odor, a little like cinnamon or nutmeg. Just to be sure of our mystery trees membership in the Myrtle Family, I held a leaf between my eye and the sun, looked closely, and saw many tiny, fragrant-oil-bearing "pellucid" dots -- a feature of leaves of the Myrtle family, like those shown below:

Psidium sartorianum, pellucid dots in leaf

Once our tree was recognized as a member of the Myrtle Family, it was easy to figure out that we had PSIDIUM SARTORIANUM, distributed from Mexico and Cuba south through Central America to northern South America. Here it grows in thin soil atop limestone.

Something else interesting about Psidium sartorianum is that the genus Psidium is home to Psidium guajava, the Guava tree whose sweet, musky-smelling fruits are much eaten in the tropics. Psidium sartorianum is described as producing fruits up to an inch in diameter (2.5cm) -- much smaller than the cultivated Guava -- but tasting something like regular guava fruits.

The tree doesn't have a commonly used English name, but in much of Mexico it's called Guayabillo, which is close enough to "Little Guava," so that's how we'll call it here. The Maya call it Niedenzu and Pichi' Che'. Reportedly the Maya traditionally used the odoriferous crushed leaves to treat cuts, stop bleeding, and promote healing. In other cultures traditional medicinal uses of different parts of Little Guava include treatments for diabetes, diarrhea, cough, pain, sores, lung problems, and more.

from the September 10, 2017 Newsletter issued from Rancho Regensis north of Valladolid, Yucatán, MÉXICO
Nowadays "Little Guava" is producing fruits that are the color of regular guavas, but much smaller -- only about as broad as a finger, as you can see below:

Psidium sartorianum, mature fruit on tree

Many species produce small, spherical fruits, but in the guava's genus Psidium the fruits bear a nicely distinguishing field mark. Below, you can see it on an unripened fruit:

Psidium sartorianum, leathery sepals atop fruit

That's what remains of the flower's sepals. In most flowers the sepals wither and may even fall away after pollination but these have become leathery and kept their place atop the flower's maturing ovary as it matured into the fruit. On fruits the sepals often are knocked off but they leave a circular scar. In the middle of the circle of sepals in the above picture, the erect item is the ovary's dried-up style.

The flesh of these small fruits shared the edible guava's texture and sweet-musky fragrance, and I wanted to see if they also tasted like guavas. However, I broke open five different fruits and they all looked like the one shown below:

Psidium sartorianum, wormy fruit

They all had worms. In the above picture, the black area consists of aborted seeds, and at the top of the blackness you can see the white grub causing the abortion.

However, I suspect that the flesh tastes like it smells, and it smells like guava. I'll bet that fruit-eating birds during the day and bats during the night gorge on these fruits, wormy or not.