The key for identification of plants is a taxonomic
key. It is an important taxonomic aid. Key can be
defined as a set of alternate characters arranged in
such a manner that by selection and elimination one
can quickly find out the name of an organism.
Depending upon the category, a key may be class
key, order key, family key, genus key and species
key.
Taxonomic keys can be of two types
(i) Indented or Yoked key
(ii) Bracketed key
Indented key provides a sequence of two or more
alternate characters from which selection and
elimination are carried out. In bracketed key, the
alternate characters are given numbers in
brackets. e.g., take three genera of family—
Ranunculaceae to explain this.
(i) Ranunculus Leaves alternate or radical,
flowers not subtended by involucre, carpels
ovuled, fruit achene.
(ii) Clematis Leaves opposite, compound petals
absent, sepals 4, carpels with one ovule and fruits
achenes.
(iii) Nigella Flowers regular, carpels united at base,
many ovules, fruit follicles.