Keys are a series of choices between two mutually exclusive and parallel statements.
Followed correctly, keys will lead you to the correct name of an unknown object.
Paired, mutually exclusive statements.
The pair of statements is referred to as a couplet.
Each 1/2 of a couplet is a lead.
Divides objects into smaller subsets until only one remains
Leaves green throughout, flowers blue.
Leaves variegated, flowers white.
Subject first, adjectives following, verbs omitted
Numbered, indented, or sometimes both
Statements should be positive
Sizes should be in measurements, not relative
Leads should be parallel
Plants villous, corollas red.
Leaves glabrous, flowers green.
Leaves villous, corollas red.
Leaves glabrous, corollas green.
Tips for Using Keys
Read both choices
Understand the terms
Try to study several specimens
If unclear try both legs
Check your conclusions