Diversity:  A relatively small group of 10 genera and 12 species that is clearly related to the Ericaceae and often placed within that family as a subfamily (see your text and Thorne's Superorder Dilleniane).

Distribution:  Throughout temperate parts of the World with extensions into the tropics at higher elevations, 2 genera with 3 species in Texas.

Floral structure:

Significant features:  These plants are easily recognized in that they differ from most other plants by the absence of chlorophyll and - at first glance - have the appearance of fungi.  They are fleshy herbs that have taken the fungal association typical of the Ericaceae to an extreme. Taxa of the Monotropaceae are myco-heterotrophic in that they use a fungal intermediate to obtain the photosynthetic product of other plants.  Thus, taxa of the Monotropaceae follow a fungal life style, spending most of their time underground only emerging to reproduce via flowers showing a structure similar to that of the Ericaceae and fleshy shoots with reduced, scale-like leaves.
    

The three Texas species: Pterospora andromeda (pinedrops - left) and Monotropa uniflora (Indian pipe - right), and M. hypopithys (far right)

Hemitomes congestum - 'Coneplant' Northwestern US/Canada

Allotropa virgata - 'Sugarstick', this plant from Washington State
 

More information on the Monotropaceae