The fruit of the western trillium (Trillium ovatum) is a green, berrylike capsule with wing-like ridges. Inside this capsule the trillium seeds are enclosed in what looks like a yellowish, sticky mass.
As I mentioned in an earlier post on the western trillium, each seed has a fleshy appendage that is attractive to ants. This fleshy structure (elaiosome) is rich in proteins and lipids. The ants take the trillium seeds back to their nests where they eat the elaiosomes or feed them to their larvae. After eating the appendage, the ants discard the seed on their “rubbish pile” where they can eventually sprout. Or if the seed is left in the nest, it is effectively planted deep in the ground.What a wonderful mechanism for trillium seed dispersal!
There are several studies in the literature which determine which species of trillium has the elaiosome that is most attractive to ants. And, of course, there are the studies to see which ants are most drawn to trillium seeds. That is a little too technical for me. I am simply fascinated by the dispersal mechanism itself without delving into the particular details. Trilliums often grow in the deep forests where there is no wind to scatter the seeds, so this is an important means by which the trillium establishes itself in new territory.
The word elaiosome comes from the Greek: “elaion” means oil and “soma” means body.
These pictures of a trillium fruit capsule and seeds with their attached elaiosomes were taken along the North Umpqua Trail in Oregon. The elaiosome does indeed look rich with oil. Pictures of the trillium flower can be found in the 5-29-2012 post entitled Western Trillium.