Date: 29th July, 2010
Assignment I
What is a Herbarium?
A herbarium is a collection of plant samples preserved for long-term study. These materials
may include pressed and mounted plants, seeds, wood sections, pollen, microscope slides, frozen
DNA extractions, and fluid-preserved flowers or fruits; all are generally referred to as
herbarium specimens. Worldwide there are over 300 million specimens preserved for research
in herbaria (plural for herbarium).
PRESSING AND DRYING PLANT SPECIMENS
Most specimens need to be pressed between several layers of paper (e.g. newspaper) under a
heavy weight for two or three weeks, or use a plant press, which consists of a wooden frame (for
rigidity), corrugated cardboard ventilators (to allow air to flow through the press), blotter paper
(to absorb moisture), and folded newspaper (to contain the plant material). The plant press is
tightened using straps with buckles or bolts with wing nuts. Change paper after two weeks. If
plants are wet, they may go mouldy and will have to be discarded. Keep labels with plants. Old
telephone books make convenient size plant presses.
The objective of pressing plants is:


To extract moisture in the shortest period of time, while preserving the morphological
integrity of the plant, and
To yield material that can be readily mounted on herbarium paper (an acid-free
cardstock) for long-term storage.
In order to fit on a standard herbarium sheet, a plant specimen should be pressed flat to no more
than 11 X 16 inches. If the specimen will not fit those dimensions, it may be folded or cut into
sections. Small loose pieces, such as seeds, may need to be placed in a small paper packet inside
of the newspaper. Large fruits or bulbs are often cut in half lengthwise or in slices prior to
pressing. Each specimen should consist of a stem with attached leaves and, if at all possible,
flowers and/or fruits. The roots of
herbaceous plants should also be
included. For the collection of weeds
roots are not required to avoid fungus
attacks. In the case of very large trees,
shrubs, or vines, pieces should be
selected to illustrate to the greatest extent
possible the overall characteristics of the
plant and the range of variation in
flowers, leaves, and other structures.
Each collection, i.e. gathering of a plant
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specimen, should be assigned a collection number. Data for
each collection should be entered in a field notebook. An
ethical collector will insure that his/her collecting activities
do not pose a significant threat to the survival of endangered
species or habitats.
Care should be taken to make good specimens. Pressing material immediately upon collection
results in the best specimens. Samples that are allowed to wilt prior to pressing will generally
produce inferior specimens. Plants should be carefully arranged as they are placed in the press
to maximize preservation of diagnostic features. Leaves, flowers, and fruits should be spread out
so that they do not overlap and can be observed from different perspectives. The collection
number should be clearly written on the outside of the newspaper containing each plant
specimen. The plant press must be kept tight; this prevents shrinkage and wrinkling of the plant
material and yields specimens that are easier to mount securely on herbarium paper. The pressed
plants must also be thoroughly dried prior to storage and mounting. A low ambient humidity
and good airflow around and through the presses also insures rapid and thorough drying of plant
material. As the specimens dry, it may be necessary to further tighten the straps on the press to
minimize shrinkage and wrinkling. Rapid drying promotes the best retention of plant color, but
excessively high temperatures or long drying periods can result in blackened, discolored, and
brittle specimens.
Take note to:
• Avoid collecting on a wet day or after heavy dew. Get the driest sample possible.
• Press evenly and flat.
• Place leaves up the same way.
• Press flowers so petals may be seen for shape, number, and arrangement.
• Label envelope or bag.
Remember!
Plants are precious! DO NOT DESTROY any plants. Collect material with great care so as not to
damage the specimen.
Herbarium specimen labels: This label should be written at the bottom corner of the
herbarium.
Family:
Genus
Species
Habitat
Plant habit
Collector’s name
Collection no
Date of collection
After every 2 weeks 15 or more different weeds should be prepared in a herbarium. In total, 50
numbers of weed should be submitted at the end. The frequency of submission will be around 4
2
times. Dead line for submission will be from the date of assignment given. Any one failing to
submit on the particular date will be given a zero mark for late submission and his/her work
will not be evaluated.
Reference:
www.flmnh.ufl.edu/herbarium/voucher.htm; 17/08/09
www.mesa.edu.au/cams/pdf/plants.pdf; 17/08/09
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