|Spigelia genuflexa leaning over to deposit its seed in the soft soil. Photo by Alex Popovkin (CC by 2.0)|
During fruit maturation, the basal infructescences bend down towards the ground, depositing the fruit on the surface (and burying it in soft kinds of ground cover, e.g., moss), whereas the upper ones do so slightly but noticeably.
This plant clearly doesn't trust that gravity will do the job appropriately. A geocarpic habit is rare but common enough to have representatives in several families. The most interesting to me about this story is that the first author of the study and one of the authors of the taxon is an amateur botanist in Brazil whose efforts have paid off. And as an aside, the guest editor for Popovkin's paper was Sandra Knapp, the botanist I mentioned earlier who was instrumental in successfully altering the botanical nomenclature code to allow online publication of new taxa.
ScienceDaily published a decent press release on this new species and the University of British Columbia's Botany Photo of the Day provided an excellent summary. (I highly recommend adding the Botany Photo of the Day site to your RSS feed.)