Use of keys for Identification

Use of keys for Identification

Key or taxonomic key is an artificial device having a list of statements with dichotomic table of alternate characteristics while is used for identifying organism. Usually a couplet or two contrasting characters are used. The one present in the organisms is chosen while the other is rejected. Each statement of the key is called lead. Separate taxonomic keys are used for each taxonomic category like family, genus and species. Two types of keys are commonly used indented and bracketed.

Indented Key. The key contains a sequences of choices between two or more characteristics. Bu careful selection of character at each subdivision  the exact name of the organism can be arrived at.

Bracketed Key. The key uses contrasting characters like the indented one they are not separated by intervening subdividing characters. Instead, each character is given a number in brackets.

We can take the example of seven genera of family Ranunculaceae Anemone Leaves alternate or radical, flowers subtended by involucres, carpels 1-ovuled, fruit achenes. Ranunculus. Leaves alternate or radical, flowers not subtended by involucres, carpels uniovuled and fruit achenes Naravelia .Leaves opposite, compound, petals, absent, sepals 4, carpels univuled and fruit achenes. Naravelia. Leaves opposite, compound, terminal leaflets modified into tendrils, sepals and petals present, carpels 1- ovuled, fruit achenes. Nigella. Flowers regular, carpels united at bese, many ovuled, follicles. Aconitum, Flowers irregular, posterior sepal enlarged to from hood, carpels free many ovuled, fruit follicles. Delphinium. Flowers irregyuar, posterior sepal enlarged to from spur, carpels free many ovuled, fruit follicles.

Herbarium

It is a place where dried pressed plant specimens, mounted on sheets are kept systemtically according to widely accepted system of classification. Herbarium is a repository or store house for future use. Every institute teaching botany, school college or university has a small or large herbarium, Very large herbaria are maintained by botanical gardens and instituted connected with plant systematic.

Every student of botany is required to collect plant specimens and prepare herbarium sheets.

Equipment

Digger and pruning knife, sickle with long handle, vasculum, polythene bags, magazines or newspapers, blotting papers, plant press, field notebook, herbarium sheets, glue, labels, small transparent polythene bags.

Method of Specimen Collection and Mounting

An area is selected for botanical excursion. It is preferable to visit the same site in different seasons. For herbaceous species the entire plant with intact parts is collected. For others, shoots having flowers, leaves and fruits are selected and cut with the help of pruning knife. Sickle with long kindle is used if the desired twigs are present at a height. Diggers are used to obtain underground parts like system, tube, bulb, corm, rhizome, etc. The collected material can be placed in polythene bags or vasculum. Vasculum is a special box with a length of 45-60 cm, depth of 25 cm and width of 20 cm. It keeps the material airtight and prevents wilting till the same is placed inside drying sheets. The collected specimens are spread over magazine or newspaper sheets. Care is taken to spread the leaves properly and to separate the petals so as to expose the essential organs. If the specimen is longer than the sheet, The same can be gently bent in n or w from. Some of the flowers are kept open so as to facilitate examination of floral parts Some of the leaves are bent to expose dorsal surface. Magazine and newspaper sheets are now put leaves the press. Plant press consists of two with straps for tightening. Detains of collecting should be jotted down In the field notebook. For this every collected material is given a member. The details include plant size, branching, root system and specialized underground organ, flower  colour, topography and date of collection. Preservative liquid used for storing fleshy organs is FAA