Excerpts from Jim Conrad's
from the June 9, 2008 Newsletter, issued from near Natchez, Mississippi:
In the campground's parking lot, right at my feet when I opened Jerry's car door, a wildflower was blooming. It was a Flowering Spurge, with little white flowers only about 1/5th of an inch across (5 mm). That's it below:
You may recall that when I was at Yerba Buena in the Chiapas highlands I described the Poinsettia's strange flower anatomy. That essay is still online at http://www.backyardnature.net/chiapas/poinsett.htm.
I'm evoking the Poinsettia because its Latin name is Euphorbia pulcherima, while our Pipes Lake Flowering Spurge is another Euphorbia species, probably pubentissima. This means that though the two plants are profoundly different in their overall aspects, their blossoms share the basic Euphorbia structure.
On the Poinsettia page linked to above the second picture from the top shows what's unusual about Euphorbia flowers. That is, the cuplike, pea-sized things that at first glance look like flowers aren't flowers at all. They're "cyathia." The actual flowers, which are unisexual, arise inside the cyathia. Moreover, female pistillate flowers, which develop into seed-bearing fruits, are too big to fit inside the cyathia, so they're set upon a stem and relegated to outside the cyathia. At the above Poinsettia link the pistillate flower hanging outside its cyathium is clearly labeled.
The Pipes Lake Flowering Spurge's flower does the same thing. In the Poinsettia page's bottommost picture yellow glands are affixed to the Poinsettia's cyathia. Our Pipes Lake Flowering Spurge's cyathia also has glands, five of them, which manifest themselves as green, flat, waxy things at the base of the white "petals," clustered near the cyathium's center. The white "petals" are actually gland appendages, one petal-like appendage per gland. Actual tiny Euphorbia blossoms don't have petals
In our Pipes Lakes picture the green, three-lobed item dangling from the cyathium is the female flower's ovary, which will mature into a fruit inside which three seeds will mature.
The little matchstick-like affairs clustered around the base of the stem of the dangling ovary at the cyathium's center are stamens. The brown, roundish knobs at the stamens' tops are anthers that open to release pollen. Since the Euphorbias' male, or staminate, flowers consist of just a single stamen, we can see that each Flowering Spurge cyathium bears several male flowers, but only one female flower.