5. 10

Taxonomic Key -- A key is a device , which when properly  constructed and used enables to identify an organism .Keys are devices consisting of a series of contrasting or contradictory statements or proposition requiring the identifier to make comparisons and decisions based on statements in the key as related to the material to be identified .

Definition -- A taxonomic key is a device for quickly and easily identifying to which species an unknown plants belong .

Structure of Key -- A taxonomic key consists of a series of choices , based on observed features of the plant specimen .

It provides a choice between two contradictory statements resulting in the acceptance of one and rejection of the other .

Taxonomic Couplet Key -- A single pair of contradictory statements is called as a couplet and each statement of a couplet is termed a lead .

By making correct choice at each level of the key , one can eventually arrives at the name of the unknown plant .

Types of Taxonomic Tree -- Two types of taxonomic tree have identified --

1 - Dichotomous --Two types -( i )Indented Keys 

                                                  ( ii ) Bracketed Keys

2 - Poly clave