Prototheca species are aerobic, achlorophyllous
, algaelike, unicellular organisms.
Subgenus Hippochaete has strobili at tips of chlorophyllous branches, whereas subgenus Equisetum possesses strobili on achlorophyllous
branches; the chlorophyllous branches are sterile.
However, more than 100 species of orchid are achlorophyllous
, which means that they are completely dependent on their fungal partners throughout their lifetime (Leake, 1994, 2005; Bidartondo, 2005).
Mycorrhiza-like interaction between the achlorophyllous
gametophyte of Lycopodium clavatum L.
The herbs are either achlorophyllous
and mycotrophic or green and autotrophic.
Leaves opposite, rarely verticillate (Curtia) or alternate (Swertia), simple, entire or reduced to scales (Bartonia and the achlorophyllous
genera); scattered mucilage cells often present in the epidermis and mesophyll; petiole without stipules but occasionally with interpetiolar line.