Current definitions of Plantae

When the name Plantae or plant is applied to a specific group of organisms or taxon, it usually refers to one of four concepts. From least to most inclusive, these four groupings are:

Name(s)	Scope	Description
Land plants, also known as Embryophyta	Plantae sensu strictissimo	This group includes the liverworts, hornworts, mosses, and vascular plants, as well as fossil plants similar to these surviving groups (e.g., Metaphyta Whittaker, 1969,[5] Plantae Margulis, 1971[6]).
Green plants - also known as Viridiplantae, Viridiphyta or Chlorobionta	Plantae sensu stricto	This group includes the green algae, and land plants which emerged within them, including stoneworts. The names given to these groups vary considerably as of July 2011. Viridiplantae encompass a group of organisms that possess chlorophyll a and b, have plastids that are bound by only two membranes, are capable of storing starch, and have cellulose in their cell walls. It is this clade which is mainly the subject of this article (e.g., Plantae Copeland, 1956[7]).
Archaeplastida, Plastida or Primoplantae	Plantae sensu lato	This group comprises the green plants above plus Rhodophyta (red algae) and Glaucophyta (glaucophyte algae). This clade includes the organisms that eons ago acquired their chloroplasts directly by engulfing cyanobacteria (e.g., Plantae Cavalier-Smith, 1981[8]).
Old definitions of plant	Plantae sensu amplo	Old classifications placed diverse algae, fungi or bacteria in Plantae (e.g., Plantae or Vegetabilia Linnaeus,[9] Plantae Haeckel 1866,[10] Metaphyta Haeckel, 1894,[11] Plantae Whittaker, 1969[5]).

Another way of looking at the relationships between the different groups which have been called "plants" is through a cladogram, which shows their evolutionary relationships. The evolutionary history of plants is not yet completely settled, but one accepted relationship between the three groups described above is shown below.^[12] Those which have been called "plants" are in bold.

Archaeplastida   Glaucophyta (glaucophyte algae)   Rhodophyta (red algae)  Viridiplantae = green algae + land plants   Chlorophyta (part of green algae)  Streptophyta   streptophyte algae (part of green algae)   Charales (stoneworts, often included in green algae)   land plants or embryophytes

groups traditionally called "algae"

The way in which the groups of green algae are combined and named varies considerably between authors.