This article is about the historic identification of plants. It shows an artificial dichotomous key system to help identification. The old artificial keys did not use scientifically correct groups. For a scientifically correct dichotomous key see Dichotomous key

Other systems include polyclave systems where the user can select appropriate characters for each unknown specimen. The user is thus free to choose any character in any sequence thus avoiding the rigid format of traditional keys.

Card key sytems have also been used. Cards with punched holes show a particular family characteristic and are selected accordingly. It is normally possible to find about 20 characteristics with good specimens. The cards are then stacked and the cards held up to the light. The logic is that families not selected are excluded from the stack thus eliminating those that do not comply.

Plant identification has evolved over hundreds of years and depends to a large extent on what criteria and whose system is used. See History of botany and History of plant systematics and a list of taxonomic systems. Plant identification implies comparisons of certain characteristics and then assigning a particular plant to a known taxonomic group, ultimately arriving at a species.

One of the most significant and useful system was devised by George Bentham (1800-1884) and Sir Joseph Hooker (1817-1911) who were British botanists working for Kew Gardens in the latter part of the nineteenth century. They devised a system in a 3 volume work, known as General Plantarium. In those books the authors presented a formal system for describing plants, which considered species with similar characteristics. A total of 202 groups were described, which they called 'orders' - now known as families. The system was renowned for being very practical and quite accurate at plant identification - but has been proven to have little cognizance of plant evolutionary history or phylogeny. Plant identification by computer programme was first introduced by Morse (1974) and successful botanical dichotomous keys now use numerical computer systems.

Study of Plant anatomy refers to internal plant structures ^[1] and is now investigated at the cellular level, involving sections, microscopy and DNA analysis. Identification is a complex process and before the advent of technology the following criteria were typically used when studying plant specimens with view to simple identification:

Appraise,

• Annual - Germinates, flowers and dies in one season
• Perennial - Lives more than two years
• Herbaceous - Without persistent wood above ground
• Woody - Structural tissue is wood

Consider,

• Phyllotaxy- leaf description
• Venation- type of veins
• Leaf morphology - Leaf arrangements

Examine type

• Flower head - with a disk of sessile flowers, example; sunflowers
• Cyathium - flowers in clusters, example; cactus or succulents
• Verticillaster - a cymose inflorescence arranged in pairs at the node, example; mint

Compare

• Actinomorphic - Symmetrical about any diameter ,star shaped example; buttercup
• Zygomorphic - Flowers symmetrical only at one place, example; orchids

Note

• Structures below the calyx - example; mallows

Observe the,

• Corolla - all of the petals, number,shape and colour
• Calyx - all of the sepals, number, shape and colour
• Tepals - undifferentiated parts of the Perianth neither petal or sepal
• Aestivation - the arrangement of flower parts in a bud before opening

Decide if,

• Polypetalae with petals free and loose, (not joined with other organs)
• Gamopetalae have the petals fused together, or more or less united, example; heather

Evaluate

• Number and position of Stamens
• Antipetalous - Flowers with stamens opposite to the petals, not alternating with them, example; carnation
• Petalous - Flowers with stamens on petals

Note

• Number of Carpels
• Style of carpel
• stigma

Consider

• Placenta where the seeds form, type and structure
• Ovule arrangement - in seed plants produces the ovules for pollination to seeds

• 
  Main parts of a mature flower
• 
  What is an epicalyx?
• 
  Ovary insertion
• 
  The life cycle of a floral plant
• 
  Different leaf arrangements
• 
  Sprouting monocot on left and dicot on right
• 
  Parts of a seed (Avocado)
• 
  A flower head type. See Inflorescence for others
• 
  Showing tendrils for climbing plants
• Stem definitions
  Stem definitions
• 
  Microscopic level of plant cells

The dichotomous key below is an indented key system, based on natural characteristics with conspicuous and obvious characteristics and it uses older taxonomic systems. There is little regard to taxonomical importance and it may not follow internationally accepted rules for botanical nomenclature. It is an artificial key. If the key ^[2] is used for identification purposes only, it is a practical method of arriving at plant major groups. The key does not continue into genus and species, but may link to other Wikipedia pages for further information.

The key starts with Angiosperms (seeds in ovary) at the top and Gymnosperms (seeds without ovary) at the bottom. By selecting one of the mutually exclusive options in the list below, chooses top or bottom and select. Then go to the next number 2 and select one option of the couplet and repeat until eventually an identification of the plant group is reached.

1 Plants with seeds, ovules (seeds) enclosed within the ovary Angiosperms

2 Flowers mostly tetra up to pentamerous with two cotyledons Dicotyledons

3 Sepals and petals are present

4 Petals are free and flowers have both calyx and corolla Polypetalae

5 Ovary is superior attached to the receptacle above the other floral parts (hypogynous), sepals seperated (polysepalous)

6 Thalamus (receptacle) is normal, dome shaped flowers Thalamiflorae

6 Thalamus expanded into a disk Disciflorae

5 Ovary is inferior, sepals united (gamospepalous)

4 Petals are fused and flowers have both calyx and corolla Gamopetalae

7 Ovary inferior

7 Ovary superior

8 Carpels - more than two Heteromerae

8 Carpels, only two Bicarpellatae

3 Sepals or petals (occasionally both absent) Monocotyledons

2 Flowers mostly trimerous with one cotyledon Monocotyledons

1 Plants with seeds, ovules exposed, not inside the ovary Gymnospermae

• John Shaffner's key (1911)in the Ohio Naturalist [1]
• Flower
• Plant morphology
• Plant physiology