Some plants do not contain chlorophyll and thus cannot make their own food by photosynthesis. They obtain nutrition from other plants, often depending on fungi to digest organic matter for them.
The plant shown here, Hypopitys monotropa, or pinesap, is not common in Colorado, but can be found occasionally in pine or spruce/fir forests. It obtains its nutrition from fungi growing on conifer roots, and thus is a parasite on the fungi. The plant is white or red while living (see image below), but becomes dark when dried and pressed as in the specimen shown at the right.
Other parasitic plants, such as mistletoe, may attach themselves directly to tree branches and absorb water and nutrients from the tree's tissue below the bark. This can weaken the tree and make it more susceptible to disease and insect damage.
To learn more:
"Parasitic Flowering Plants" at Wayne's Word: An On-line Textbook of Natural History