Introduction

In order to answer the question in the title right away:

- 2 families, 2 genera and 4 species of Bryophytes,
- 1 Gymnosperm,
- 6 families, 26 genera and 295 species of non-orchid monocots,
- 44 genera and 328 species in Orchidaceae
- 3 families, 17 genera and 52 species of eudicots.

This sums up to
13 families, 90 genera and 680 species of mycoheterotrophic plants. (18th of October 2023)
For more specific statistics see here

Mycoheterotrophic plant species (MHP, Leake 1994) lack chlorophyll and depend on their mycorrhizal fungus for carbon and nutrient supply. MHP were first counted by Johow (1889), who estimated 160 species of “achlorophyllous humus plants” in 43 genera and 5 families. Schmucker (1959) already counted 352 “holosaprophytic” species in 48 genera and 6 families. Furman and Trappe (1971) referred to “roughly 400 species”, 50 genera and 7 families. In an review on MHPs Leake (1994) lists 417 MHP species in 87 genera and 11 families. My own preliminary reassessment of Leake's list in 2008 resulted in 438 species/84 genera/10 families, but was just a rough estimate. Merckx (2013), in his introducing chapter to the first book exclusively dedicated to MHP (Mycoheterotrophy - The Biology of Plants living on Fungi), rates: "At least 514 species of angiosperms and a single liverwort species entirely depend on fungal carbon during their complete life cycle".

This website aims to provide a list of all mycoheterotrophic plants on earth, combined with additional information such as synonymy, taxonomic history and bibliography. This account is now complete, as far as it came to our knowledge (Stephan Imhof and Jakob Zoller). We appreciate every hint on newly described species or taxonomic changes we might have overseen.
The criterium to be included in this list is "optical achlorophylly" or at least nearly such. We are aware of intergrading dependences on the mycorrhizal fungus even in green plants (see the pages The case of Pyrola aphylla, Obolaria and Bartonia or Stemona aphylla), as well as of different amounts of chlorophyll content  (several Burmannia spp., Polygala setacea or Salomonia ciliata), which often is even hidden by other colouring compounds (e.g. Neottia nidus-avis). For example, Holopogon pekinensis (treated as Neottia pekinensis in Wang et al. 2023) , described in Mu et al. (2017) with obviously green axes and flowers, is not included here.
Under the flag 'Mycoheterotrophic Plants' you find a taxonomic tree, where synonyms appear ahead of the accepted taxa, each of which in alphabetic order. The flag 'Literature' collects the bibliographic data of the taxonomic literature mentioned, as well as other articles dealing with all aspects of mycoheterotrophic plants (1862 references so far). The citations in the taxonomic comments (pages) are hyperlinked with the bibliographic data. You find the taxonomic comments under the flag 'Descriptions' when choosing a species name in the taxonomic tree 'Mycoheterotrophic Plants'.

If you want to cite this website we suggest the following pattern: Imhof, S. (year accessed): Mycoheterotrophic plants - How many of them are there? Accessed at mhp.myspecies.info on date xx.xx.20xx.

If you want to cite a particular page/article I suggest: 'Author of the article' (year of the article): 'Title of the article'. In: Imhof, S. (year accessed), Mycoheterotrophic plants - How many of them are there? Accessed at mhp.myspecies.info/node/xxxx on date xx.xx.20xx.