Albino redwood trees

Albinism is rare in humans and animals, and it is rarer still in plants, where it manifests as the complete lack of chlorophyll. Because this green pigment is vital to the manufacture of food and thus the survival of plants, an albino plant typically die as seedlings.
There is an exception, however... several albino redwoods in California that have managed to survive till adulthood by latching on to the parent redwood and leaching off nutrients from the host tree...
New research have suggested that the albino redwood also helps the healthy redwood trees to survive by filtering out toxins from the soil. Albinos have defective stomata that causes them to lose more water through transpiration, forcing them to compensate by taking up more water through their roots. As a result, they accumulate more metals in their bodies than normal trees do... The research led by Zane Moore, a doctoral student at the University of California Davis, found high levels of toxic heavy metals, including nickel, copper and cadmium. These heavy metals were at least twice as high in the albino redwoods compared to healthy redwood trees...
It is believed that there are about 400 albino redwoods across California’s wilderness. Their locations are not advertised in order to prevent people from seeking them out and collecting souvenirs that would be harmful for the plant.
There's more information and several great pictures at Amusing Planet.