COLLECTION AND IDENTIFICATION OF PLANTS
Reference: Handbook of
field and herbarium methods by Jain S. K. and Rao, R. R.
Plant collections generally consist of samples of plants that are preserved by drying
or by means of liquid preservation. They may also include live plants or
propagules taken from the wild and grown in artificial environment.
Botanical collection refers to any process of gathering plants from the field for
various purposes. The nature of the collection varies with purpose. Plant
collections serve several purposes:
- They are used for building up a new herbaria or for enriching the
already existing one (old herbaria)
- Plants are collected for class work/teaching or for donating to other institutions.
- For introduction of live material in gardens or for breeding
studies.
- Collecting large quantities of a
particular plant for crude drug
for trade
- For ethnobotanical studies (study of relationship of plants with
local inhabitats of an area, noting their uses, taboos e.t.c.)
- For sale or trade.
- For research work or analysis
- Used in studies of floristic
diversity –writing up flora of a given area.
- They serve as reference material for
named taxa. Such reference materials are termed as voucher specimens. Most are dried specimens and they are
selected from the original plant collection (type specimen)
- Voucher specimens may serve as
reference in verifying the identity of a plant taxon.
Kinds of field work
This depends on
the purpose of plant collection but can broadly be:
(a) Collection trip- covers a small nearby
area and lasts for a day or few days. The purpose is for detailed study of the
vegetation or flora of the area.
(b) Exploration- lasts for 4-6 weeks and
covers a bigger area such as a district; for detailed floristic studies and
building up herbaria and to study plants of economic importance. It requires a
lot of planning and preparation.
(c) Expendition- lasts for several months
and covers a bigger area. It takes place in remote places which may be
difficult to reach and involves a lot of preparation; generally done in groups
involving several institutions or organizations; costs a lot of money; area may
usually yield new species; needs a lot
of coordination in terms of funding, communication, supplies, publicity,
leadership , allocation of duties and safety.
Preparation
This calls for prior arrangements depending on purpose, duration,
size of the party and the area they are visiting. However you need to:
(a)
Study the area before the trip – use
literature, published pamphlets (floras), maps. If collections are in protected
areas e.g. national parks, request for permission to collect plants should be
made prior to the visit of such areas.
(b)
Make arrangement of journey and where to
stay – communicate with the relevant authorities for accommodation reservation,
especially in remote areas. Plan to stay in affordable and decent places e.g.
guest houses, hostels, campsites, hotels etc. Such places should have adequate
space fro sorting out plants collected during the day and press them.
(c)
Equipment/materials – These are the
things you will need in the field. Some of the general equipments required
include the following:
(i)
Vasculum – this is a metal or aluminium
tin with a tight lid for keeping plants immediately after collection and is
painted white to deflect heat. In the absence of this polythene bags of
different sizes can be used.
(ii)
Field/plant press – This is a device by
means of which fresh specimens are pressed and quickly dried. It is made up of
two simple hard boards or thin plywood or from wires measuring 30x42cm and tied
using a leather or cotton straps. In between are placed a number of driers or
blotting papers containing plant specimens.
(iii)
Field books – these are special books
that are used for labelling plants as well as recording notes about plants in
the field. Many herbaria and professional collectors have form-style collecting
books with printed serial numbers. Carbon copies of field notes are made on
perforated pages. These pages are torn out and placed with specimens when they
are pressed. The original is retained in the notebook and kept for records. In
their absence, ordinary exercise books can be used.
(iv)
Blotting paper/absorbent papers/newspapers – these are used for pressing and drying specimens. One needs to
carry a lot of them if staying for long in the field. Valuable data such as
collection no’s, dates or any other information should never be written on
these papers as they are frequently changed. It is always preferable to have
labels stuck on plants instead.
(v)
Specimen jars/tubes/bottles – these
should be assorted sizes and filled with fixatives (e.g. FAA for preserving
plant tissues; carnoys fixative for cytological material such as flower buds,
root tips and 70% ethanol for morphological studies. For DNA studies silica gel
used for preserving plant materials. The specimen bottles/jars must be clearly
labelled with the species name and collector number.
(vi)
Shoulder bags/backpacks – these are made
of canvas or some waterproof material. They are used for keeping items such as
cameras, binoculars, secateurs, notebooks, water bottles, GPS etc.
(vii)
Secateurs – or clippers for cutting
small twigs from trees and shrubs fro the herbarium.
(viii)
Pruning shears – for cutting twigs from
tall trees
(ix)
Pick or small shovel – for uprooting
herbaceous or bulbous plants for the purpose of identification. To avoid loss
of equipment in the field, one should paint the equipment’s handle a bright
colour.
(x)
Global positioning system (GPS) – for
collecting field data such as longitude, latitude, altitude etc.
(xi)
Magnifying lens – preferably x10
magnification.
(xii)
Pens & pencils, Photographic equipment (digital camera), First
aid kits 9with medicines for insect bites, snake bites etc), field shoes,
utensils, food stuff, match box etc.
What to collect
Depending on the purpose of collection, all collections should be
exhaustive and samples of all plants should be collected. Materials collected
should be good, properly labelled, well pressed and presentable. What one
collects depends on the purpose of the study. A collection should comprise of
good specimens which:
(a)
Contain flowers or fruits or
both and should be clearly displayed on the pressing sheet without unnecessary
folding or hiding of parts. Sterile specimens should be avoided.
(b)
In case of small plants like
grasses, sedges and other herbs, whole plants including underground parts
should be included.
(c)
Flowers, fruits and twigs
should be taken from the same plant.
(d)
Try to collect flowers of both
sexes even if they are on different plants
(e)
All groups of plants must be
taken to make collections complete and representative including mosses, ferns
and lichens.
(f)
Collect a good material which
is free from disease and deformity
(g)
Collect several plants of the
same type/species. The number collected should be at least six to facilitate
distributions and exchange.
Factors to consider when
collecting plants
(a)
Be able to recognize sensitive species i.e. those that are rare, threatened or endangered. Most of these are protected
by law and may not be harvested without permits.
(b)
Any collecting should not
endanger the local population. Apply ‘1 to 20’ rule: for every one plant sample
you collect, there should be at least 20 more present in the surrounding population.
(c)
Size of plant specimen- The
card (mounting sheet) on which plants are mounted is 28 x 42 cm in size and
your plant should fit in it. It the plant is bigger than this then fold it into
V, N, M or Z shapes. For small herbs whole plants are collected and for large
plants, part of the plant are cut and labelled A, B, C, D etc.
Documentation of plant
collections or Field notes
Certain data must be recorded at the time of collecting a plant. The
information is recorded in the field notebook and it is eventually typed onto
the herbarium label. The data includes the following:
1. Flora of: give country, province, district etc.
2. Vernacular/local name: should be
obtained from reliable sources to avoid exaggerated names and the language
should be included.
3. Locality: name of place, the
approximate distance and direction from a permanent place. This should be as
detailed as possible, including the name of roads, lakes and so on in the
vicinity, as well as Township and District. The latitude and longitude or the UTM Grid Reference and Map Number will
be needed fro the herbarium label, but can be added later if they are not
known. One can also use the Global Positioning System (GPS) as it helps one to
quickly get the latitude, longitude, altitude and other data much faster.
4. Habitat: this refers to the condition
under which a plant is growing e.g. marshland (swamp), moorland, thicket,
forest, rock crevices etc. This should include the general habitat as well as
more specific details of micro-habitat. Important points are type of soil or
other substrate (sand. Clay, granite, dead wood, other vegetation), associated
species, moisture and aspect (fully exposed on a south facing bank; under dense
scrub etc).
5. Description
of the plant: this should be brief; visible variations that are not obvious
on the herbarium specimen. State the height; annual or perennial; erect or
prostrate; herb, shrub or tree; type of bark; obvious smell; whether plant is
clomped, single or growing in patches and the presence of creeping or
underground stems; flower and fruit colour; pubescence; latex etc.
6. Economics or uses: note whether any
part of the plant is edible or poisonous; whether the parts of the plant are
useful e.g. in making timber, medicinal etc.
7. Frequency: is plant common or rare
8. Collector’s name: should be written in
full
9. Collector’s number: should consist of numerical series from
number one and continuing in that sequence. Each specimen should have its own
number written on a label and attached to it.
10. Date of collection: give the date,
month and year to avoid confusion.
After all this information is recorded, the collected specimens are
pressed and taken to the herbarium fro identification and documentation.
Pressing and Drying of the
Specimen
Plant pressing – is the process of drying plants in a plant press between
absorbent papers. The purpose is to flatten and dry the specimens. Usually:
i)
Collect a good material which
is free from diseases, deformity etc.
ii)
Place one plant per folder of
drying paper.
iii)
Fold herbaceous plants which
are longer than 30 cm (M, N, Z).
iv)
Prune to avoid overlapping
parts.
v)
Press with some leaves facing
up and others down. This is good especially for ferns. For bulbs and other
bulky plants, press after removing extra tissue.
vi)
If seeds and fruits are
collected they should be mature and they should be dried and kept in a pocket.
vii)
For large plants, photograph,
make sketches and collect seeds, flowers, branches etc.
The Plant Press
The plant press is designed so that plants can be dried quickly
while being pressed flat. It consists of two cross-slatted wooden frames about
the size of a folded newspaper (30 x 42cm). Plant specimens are laid in folded newspaper between layers of blotter sheets or foam and corrugated cardboard. The newspaper
provides a folder for the plant. The
paper, blotter and foam draw the moisture away from the specimen. Blotters can
be thick blotting paper or thin sheets of the polyurethanefoam that is laid
down under carpets. Foam is best for woody species or plants with large fruits,
because the foam adjusts to the contours of the thickest parts of the specimen
while at the same time ensuring that the leaves are well pressed. The cardboard
allows air circulation within the
press to speed up the drying process, and helps keep the specimens flat. Plants
in their newspaper folders are piled in layers of alternating blotter and
cardboard on one of the wooden frames (i.e. cardboard – blotter – folded
newspaper with plant inside – blotter – cardboard – blotter – etc). When lying
of the specimens is complete, the second frame is laid on top of the pile which
is compressed and strapped as tightly as possible. The press is then placed to
dry in warm, dry, circulating air. After 24 hours the paper and blotters should
be changed to enhance the drying process. After this, the specimens may be left
undisturbed for several weeks or months until they are completely dry and the
press can be emptied. The straps have to be tightened periodically as the plant
material shrinks.
Procedure for Pressing
Plants
When preparing plants for pressing ensure that the dried specimen
should fit neatly onto a standard herbarium sheet (420 x 297 mm; and as many
features as possible should be visible on the mounted specimen. The following
steps should be followed to help produce attractive and worthwhile mounted
material:
- If a specimen is too long (longer
than 30cm) to fit in the press or on the herbarium sheet, make a zig-zag
bend in the stem or fold them in form of N, M, W, Z. This shortens the
length of the specimen without any of the material being lost.
- Many leaves on a herbarium sheet
look untidy and obscure detail. Snip off some of the leaves but always
leave part of the petiole so that it is evident that leaves have been
removed.
- The specimen should be laid out so
that there is little or no overlap between parts.
- When stems are very thick they can
be sliced lengthwise so that they are less bulky.
- If there are several flowers on a
specimen, some should always be pressed open and flat so that the inside
is displayed.
- Loose seeds and fruit can be placed
in a small paper packet and pressed with the specimen. Later this packet
will be glued to the herbarium sheet.
Mounting of the Specimen
Once the material is pressed, thoroughly dried, and poisoned, it is
mounted on herbarium sheets. Poisoning can be done with mercuric chloride or
formalin. Sometimes plants are fumigated using paradichlorobenzene. The
standard size of the herbarium sheets is 420 x 297 mm. They should be made from
stiff, acid-free paper or cardboard of good quality so that they do not turn
yellow or crack with age. Space should be left in the lower right hand corner
of the sheet for the herbarium label. When the arrangement is satisfactory, the
specimen may be stuck to the sheet. Elmers glue or wood glue is often used to
fix the plant on the herbarium sheet in such a way that all parts of the plant
are visible. Usually one specimen is mounted per sheet of paper. A herbarium label (8 x 10cm) is then glued on
the bottom right hand of the sheet with all the information from the field note
book e.g.
Flora of:
Name: Scientific
Vernacular
Locality:
Habitat:
Collectors Name:
Collectors Number
Date of Collection:
After mounting and labelling
of specimens, the next step involves identification.
Plant Identification
Is the process through which an unknown plant is determined as being
identical or similar to another already known plant. In this process the
correct name of the plant is determined. Identification of plants is
accomplished by use of different methods. The three major ones include the
following:
(a) Use of Herbaria (Specimen
Comparison)
A herbarium is a collection of plant specimens that have
been dried, identified and arranged systematically and they are available for
reference or other scientific study. In this method an unknown plant is
compared to an already correctly named herbarium specimen or a living collection.
This method is only useful if we have a rough idea about the unknown plant such
as family or genus thus narrowing down on the possibilities of identifying the
taxon.
(b) Use of Taxonomic
Literature
These are written accounts which include floras,
checklists, taxonomic revisions etc which contain keys and descriptions of
plants growing in a given geographical region. Features of the unknown plant
are compared with written descriptions of the possible known taxa. This is a
good method of determining with certainty whether the range of variation of the
unknown plant corresponds to that listed in the description of a known plant.
(c) Use of Taxonomic Keys
(Botanical Keys)
A taxonomic key is a device or method used to determine
the identity of an unknown plant when the comparative methods have failed. A
key is useful only if we have a rough idea of what the unknown plant is e.g. the
family or the genus.The user of the key is presented with a sequence of
choices, usually between two statements until she/he arrives at the name of the
unknown plant. The statements in the choices are based on the characteristics
of the unsown plant. If the plant is a flowering one, the vegetative or
flowering parts or both are used in identification e.g. flowers, fruits, seeds,
stems, leaves, roots etc. Keys that are dichotomous (forked keys) with only two
contrasting characteristics or statements are preferred to those that offer
several equal statements to choose from.
A pair of contrasting statements in a key is called a couplet. Each statement in a couplet is
termed as a lead. The main type of
key is the forked or branching or dichotomous keys. It is of two kinds: the indented and the bracketed or numbered keys.
Indented keys are those where the contrasting statements or couplets are printed
with gradually increasing indenting.
Indented key layout:
1 --------------
2
------------------
3
------------------
3 ------------------
2 ----------------
1 --------------
Example
1. Fruit a group of akenes; flower not spurred
2. Petals none
3.
Sepals usually 4; involucre none ------------------------- Clematis
3.
Sepals usually 5; involucre present ---------------------- Anemone
2. Petals present
-------------------------------------------------------- Ranunculus
1. Fruit a group of follicles; Flowers spurred
4. Flowers regular;
spurs 5 ------------------------------------------- Aquilegia
4. Flowers
irregular; spur 1 ------------------------------------------ Delphinum
The first choice is between “Fruit a group of akenes; flowers not
spurred” and “Fruit a group of follicles; flowers spurred”. These paired
statements are given the same indention and the same number. If the latter
choice is taken, the next choice, as shown by indention and the number is
between “Flowers regular; spurs 5” and “Flowers irregular; spur 1”. Therefore
if the plant in question has follicles and irregular flowers with a single
spur, it must be Delphinium.
Bracketed keys are keys where the two contrasting/alternative statements or
couplets are written in adjacent lines giving reference by numbers of their
successive subordinate clue or couplet.
1. Fruit a group of akenes; Flowers not
spurred ---------------------------------- 2
1. Fruit a group of follicles; Flowers
spurred ------------------------------------- 4
2. Petals none
-------------------------------------------------------------------------- 3
2. Petals present
-------------------------------------------------------------- Ranunculus
3. Sepals usually 4; Involucre none
--------------------------------------- Clematis
3. Sepals usually 5; Involucre present
------------------------------------ Anemone
4. Flowers regular; Spurs 5
------------------------------------------------- Aquilegia
4. Flowers irregular; Spur 1
------------------------------------------------ Delphinium.
NB: The number at the right
end of a line in the bracketed key indicates the next numbered pair of choices
to be considered.
When using keys ensure that:
a)
The alternating clues are clear
and contrasting.
b)
When measurements are given, do
not guess; take the measurements
c)
Always read both choices
d)
Be sure you understand the
meaning of the terms involved. Do not guess.
e)
Finally check the conclusion
with detailed description of the plant and see if it agrees with the unknown
specimen.
In contrasting
keys, take note of the following:
a)
Use constant characteristics
rather than variable ones
b)
Use measurements, not words
such as large or small.
c)
Use characteristics that do not
change with season
d)
If possible start both choices
of a pair with the same word and always capitalise the first word.
e)
Precede the description terms
byb the name of the part which they apply e.g.
I.
“Flowers red or purple “but not
“Red or purple flowers”
II.
“Leaves toothed” and not
“Toothed leaves” etc.
f)
Construct a chart of objects to
be keyed before constructing the key itself.
g)
After constructing the key read
the description to see if it fits with the unknown specimen.
h)
Compare the unknown specimen
with authenticated specimen in a herbarium.
Other methods of identification include: image comparison (visual comparison of specimen to photographs and
illustrations); expert determination
(asking an expert who is familiar with the group of plants under study).
