One of the important purposes of the study of External Morphology is to be able to
describe a plant completely and correctly.
Without such a description it is not possible to identify a
plant and to ascertain its place in the plant kingdom, i.e. to assign it to its
family, genus, species etc.
To describe a plant a student should follow the scheme given
below. It will be seen that to make his description accurate, the student will
have to exercise all his knowledge of Morphology.
Habitat: Locality with
latitude, longitude and altitude. The natural climatic and edaphic environment
of the plant, namely aquatic or terrestrial, type of soil or rock (sandy,
calcareous, etc.), bright sunshine, shade, desert conditions, etc.
Habit: Epiphyte,
parasite, etc.; herb, shrub, tree, climber; annual, biennial, perennial;
succulent, woody, deciduous, evergreen; size, etc., general characters of the
whole plant.
Root: Tap,
adventitious, or any special type etc.
Stem: Characters
not included under habit.
Branching.
Surface of
stem – glabrous, hairy, etc.
Colour of
stem.
Shape –
round, square, ribbed, etc.
Hollow or
solid, jointed or not.
Any special
modification – phylloclade, etc.
Leaf: Phyllotaxy.
Insertion – radical or cauline, petiolate or sessile,
peltate, etc.
Simple or compound – type of compound.
Leaf base – stipulate or exstipulate, kind of stipule,
any
speciality.
Petiole – any speciality.
Leaf lamina – shape, venation, margin, incision, apex, base,
surface, texture, glands, colour, odour and taste.
Modifications and specialities (ligule, stipel, heterophylly,
etc.)
Inflorescence: Type –
racemose, cymose, etc.
Flower:
General: Bracteate or
ebracteate – type of bract.
Bracteole – if any.
Sessile or pedicellate.
Complete or incomplete – dichlamydeous, monochlamydeous,
achlamydeous, etc.
Bisexual or unisexual – monoecious, dioecious, etc.
Symmetry – regular, zygomorphic or assymetrical.
Floral phyllotaxy – cyclic, spiral, hemicyclic.
Insertion – hypogynous, perigynous, epigynous.
Erect, pendulous, etc.
Size.
Any speciality – disc, nectary, etc.
Thalamus: Any
speciality not included under flower.
Calyx: Cohesion –
polysepalous or gamosepalous.
Number of sepals or lobes.
Superior or inferior.
Aestivation.
Calyx shape – sepal shape.
Size (of calyx and sepals).
Colour.
Duration – caduceus, deciduous, persistent.
Any speciality (modification, appendage, etc.)
Corolla: Cohesion –
polysepalous or gamosepalous.
Adhesion.
Number of petals or lobes.
Superior, inferior.
Aestivation.
Corolla shape (regular or irregular) – petal shape.
Size – corolla and petals.
Colour, duration, texture, scent.
Perianth: (When
calyx and corolla cannot be distinguished).
Sepaloid or petaloid.
Other characters as in calyx and corolla.
Androecium: cohesion –
in filament, in anther, in both.
Number – fertile and sterile ones as also separate whorls
separately counted.
Adhesion – with corolla or gynoecium.
Superior or inferior.
Filament – any outgrowth, sessile or not, length.
Anther – attachment of filament, dehiscence, introrse or
extrorse, number of pollen sacs, appendages.
Pollen- powdery, etc; appearance; pollinia.
Colour.
Speciality – didynamous, etc.; obdiplostemonous, etc.;
exserted or inserted; nectaries, etc.
Gynoecium: Cohesion –
apocarpous, syncarpous, etc.
Number.
Adhesion – with Androecium.
Ovary – shape, number of loculii, placentation, superior or
inferior.
Style – number; free or united; terminal, lateral, gynobasic,
etc.; shape; size; colour; any peculiarity.
Stigma – number; sessile or not; shape – simple, lobed,
branched, etc.; smooth or papillose; any speciality.
Ovule: number; number in each loculus; ascending, horizontal,
etc., anatropous, campylotropous, etc.
Any speciality in the gynoecium.
Floral
Diagram & Floral Formula.
Pollination: Type if
observed.
Fruit: True or
false; dry or fleshy; dehiscent or indehiscent.
Type of fruit, manner of dehiscence (if dehiscent).
Size.
Any speciality (edible, poisonous, etc.; which part edible).
Seeds: Number of
seeds in fruit.
Morphology – perisperm, endosperm (nature of food reserve),
embryo.
Size and shape.
Any speciality (aril, etc.)
Manner of germination.
Method of dispersal.
·
Any
description should be accompanied by neat and representative labelled
sketches/diagrams/figures.
