The Plant That Forgot It Was a Plant
On the floor of Brazil's Atlantic forests, a strange organism pushes up through the leaf litter. It has no green parts, no leaves, and its fleshy, rounded form looks for all the world like a fungus. This is Scybalium fungiforme, a name that literally means "fungus-shaped." For a long time, its appearance fooled observers. It belongs to the Balanophoraceae, a family of bizarre flowering plants that have abandoned photosynthesis entirely.
Scybalium fungiforme is an obligate holoparasite. This means it spends almost its entire life underground as a lumpy, tuberous structure fused to the roots of a host plant, siphoning off all the water and nutrients it needs to survive. The plant lacks chlorophyll and has no root system of its own, instead using a specialized organ called a haustorium to penetrate its host. This parasitic lifestyle has led to the loss of typical plant features, a example of convergent evolution where it has evolved to resemble the fungi that share its dark, subterranean habitat. Its main hosts are fast-growing lianas and a pioneer tree species, Croton floribundus. The visible "mushroom" is actually a dense inflorescence—a structure packed with tiny, unisexual flowers that can reach about 8 cm in diameter.
An Opossum's Secret Garden
The floral structure of Scybalium fungiforme presents a puzzle. The nectar-rich flowers are hidden beneath tough, scale-like bracts, making them inaccessible to most insects. In the 1990s, botanist Patrícia Morellato theorized that a mammal with dexterous hands might be important. Her hypothesis was based on pollination syndrome—the idea that a flower's traits reflect its primary pollinator. The flower's low-to-the-ground position, copious nectar, and tough covering all pointed to a non-flying mammal.
Decades later, in 2019, night-vision cameras finally confirmed her prediction. The footage captured big-eared opossums (Didelphis aurita) methodically using their opposable thumbs to peel back the bracts, push their faces into the inflorescence to drink the nectar, and emerge with pollen-dusted snouts. As the opossums move from one plant to another, they achieve pollination. Once the bracts are removed, a host of secondary pollinators can access the now-exposed flowers, including bees, wasps, hummingbirds like the Violet-capped Woodnymph (Thalurania glaucopis), and even the montane grass mouse (Akodon montensis). This complex web of interactions, with an opossum as the primary facilitator, is a pollination strategy that took nearly 30 years to prove.