Now there is the matter of how a flowering plant without chlorophyll obtains energy and nutrients. Three plants are involved, in the case of the Indian Pipe, or Monotropa uniflora: a tree, a fungus, and the Monotropa. The tree and the fungus mutually benefit each other, the tree providing energy, in the form of sugars, and nutrients to the fungus, and the fungus providing nutrients and even water to the tree. The Monotropa has a purely parasitic relationship - it takes sugars, minerals and nutrients from the fungus, as well as nutrients that the fungus has gotten from the tree, providing nothing in return. And so the energy source for the Monotropa is a tree, by way of a fungus!

The trees involved in this relationship are most often conifers - pine, spruce and fir, also beech, oak and cedar. The fungus may be Russula or Lactarius mushrooms, and probably others. Russula and Lactarius mushrooms are closely related. Pictures of the two can be see at first-nature.com fungi.

There are some details with this relationship between Monotropa, mushrooms and trees that are nice to read. There are many references to the sharing and acquisition of nutrients and carbohydrates between the three players, but not so much on the specifics - what are these nutrients, and how is it that one player is better at acquiring certain nutrients than the others. I found a reference, written by David Moore, an academic, and at level just right for me - a good scientific basis, but not the rigorous detail of the area of study. These are the definitions and explanations that were most frustrating to me as I read through the many Internet sites discussing the Indian Pipe and it fungus / tree relationship, explained on David Moore's site.

Mycorrhizal association - a fungus that grows in association with the roots of a plant in a symbiotic or mildly pathogenic relationship. Myco - fungus; Rhizosphere - a plant's root system.

In a mycorrhizal association, the fungus that colonizes the plant's root tissue is, at the cellular level, extending root processes, hyphae, into the cell of the plant. This may be intracellular, with the fungal hyphae invaginating the cell membrane, or extracellularly, invaginating but not penetrating the cell wall. In any case, the surface area between the fungal hyphae and the plant is greatly increased, allowing for transport of nutrients between the plants.

In the mutualistic association between fungus and tree, the fungus receives carbohydrates such as glucose and sucrose, while the tree gains benefit of the mycelium's higher absorptive capacity for water and mineral nutrients such as phosphate ions and micronutrients such as iron. The fungus can also mobilize nutrients from organic matter that is slow to decay, such as wood.