Excerpts from Jim Conrad's
from the the August 9, 2009 Newsletter, issued from the Siskiyou Mountains west of Grants Pass, Oregon:
PORTULACA'S BOWL OF JEWEL-LIKE SEEDS
The Portulacas, or Rose-Mosses, PORTULACA GRANDIFLORA, in Anita's rock garden, do none of that. Their manner of setting the seeds up for being knocked from the mature fruit is amazing. But, first, look at Anita's pretty serpentine-rock-garden Portulacas above.
Above the close-up shows a flower's bunch of stamens consisting of orange, pollen-releasing anthers atop slender, stiff, dark-purple filaments, with the several-parted style looking like a star-burst at the far right, each style arm ending in a fuzzy stigmatic zone where pollen grains are supposed to germinate. The style arms unite and lead down to the oval ovary hidden by the stamens.
Once ovules inside the ovary are fertilized by the male sex germs, the corolla dries up and shrivels as the ovary grows to approximately the size of a pea. When the shriveled corolla falls off, the ovary remains, now a mature fruit, and here's the thing I'm referring to that's amazing about it: It looks like a can opener has cut a slit around its circumference. Instead of splitting lengthwise like normal dehiscing fruits, this one splits around its middle. Take a look at the picture below:
The red "bowl" there is the bottom of the ovary. The white rim is scar tissue where the top half has come off. And the bowl is filled with shiny, finely ornamented, jewel-like, black seeds.
Pods that dehisce around their middles like this are said to be "circumscissile," and a more elegant way of offering up seeds to be scattered in a world of hard knocks can hardly be imagined.