This is a genus of only ten species all of which apart from Corallorhiza trifida, are exclusively north American.
The species are all saprophytic and depend on mycorrhizal fungus for the majority of their nutrition, they do however maintain a significant amount of chlorophyll in their their stems and are therefore able to manufacture some of their food via photosynthesis.
This capability accounts for the greenish coloration of the plants and in the case of Corallorhiza trifida, serves to differentiate it from the other European saprophytes which contain no chlorophyll at all. Unlike these species however, it rarely reproduces vegetatively and relies almost entirely on self pollination.