The following points highlight the seven main steps to be followed for collecting the plant specimens. The steps are: 1. Planning 2. Pressing 3. Drying 4. Poisoning 5. Mounting 6. Labelling 7. Storing.
Step # 1. Planning:
Proper planning and making arrangements before undertaking a long trip is essential.
The following points may be followed:
1. Try to get available maps and collect local information.
2. Try to have best guide and for carrying the equipment select preferably people who are more or less acquainted with forest work. The local forest rangers and forest guards are of great help.
3. Calculate the food you must take with you especially the fast food. Keeping in mind that a porter will carry about 15-18 kg. excluding his personal belongings.
4. Try for camping in Forest Rest House or Travellers Bungalow.
The equipments for field work vary in different situations.
The important ones are:
1. A collecting pick for digging up roots and rhizomes of herbaceous plants so that the collected specimen is complete.
2. A strong knife or machete is sometimes required for cutting branches and other plant parts.
3. A pair of pruning shears or secateurs for cutting woody and hard material.
4. A pair of forceps for flower bud study.
5. A vasculum for accommodating collected specimens.
6. A plant press with blotters or newsprint for pressing and keeping the collected specimens.
7. Several spare sheets of blotting paper (blotters).
8. A filled book (field diary) for noting down the details of collected plants.
9. Tags of thin tin or aluminium. The tag is numbered and tied to specimen in the field. This number should correspond with the number of the page of field book on which details of plant was noted.
10. Polythene bags or collecting bags. These are convenient containers for fresh plant specimens. After storing plants in these bags, the mouth of bags should be tightly closed to avoid wilting of plant material.
11. Hand lens and pocket lens.
12. Camera and film.
13. Field press, folders of absorbent tissue papers or even newspapers.
14. General equipments – First aid box, food stuff, water container, Haversack (Shoulder bag), pen, pencil etc.
The data accompanying the specimens are as important as the specimen itself, badly labelled material being more of hinderance than a help. The main objective of field notes is to record data of taxonomic value that will not be apparent from the specimen.
The following details should be recorded in field not book:
2. Number of plant – a serial number or collector’s name and number or collector’s name, year and number
3. Name of plant (as far as known – even if only to family).
4. Province – or whatever major divisions of country you wish (e.g. state, or district).
5. Locality – name of the place, distance and direction with reference to familiar or known place.
6. Altitude – in metres.
8. Description – Chief characters of specimens viz., colour of flower, aroma, latex, size, curious characters.
Handling of fresh material:
There are three important methods of handling freshly collected plant material viz.:
1. To press each plant as it is collected in the field then and there.
2. To keep all the specimens collected in a vasculum and bring them to camp. They are then pressed one by one.
3. This method is used more in the tropical rain forests than to temperate regions, is to carry collected specimens in a rucksack and brought to the camp where they are pressed.
Step # 2. Pressing:
Pressing is the process of placing specimens between the absorbent drying paper under heavy pressure in a plant press. Corrugated cardboard can be inserted between the drying paper to even out the pressure and to facilitate the aeration of the press. Pressing is most important step in the preparation of specimen and needs careful attention.
The specimens should be carefully selected before pressing and the following points may be taken note of:
1. Underground parts like root, rhizome, etc., must be included in herbs.
2. Roots and underground parts should be washed thoroughly before pressing to remove soil particles.
3. Select specimens in flowering or fruiting stage.
4. Ensure that specimens are free from insect feeding, fungal infection and any pathological symptom.
5. Fresh specimens should be arranged within the pressing paper.
6. Maximum surface of pressing paper is covered with the plant specimen to be pressed.
7. Single specimen should be pressed in a folded pressing paper.
8. Herbaceous specimens, longer than 40 cm, may be folded in to V-shaped, N-shaped or M-shaped manner and then pressed.
9. Care should be taken to press the plant parts attached to the plant in their natural position.
10. A few leaves should be arranged with their lower surfaces facing upward.
11. A few flowers should be pressed separately of the specimens with gamopetalous corolla. Some of the flowers should be split open and then pressed to expose their essential organs and the nature of the thalamus.
12. Fleshy and bulky organs should be sliced open to facilitate quick drying. Paper padding or cotton batting around such organs is helpful for drying.
13. To avoid decoloration and moulding, blotters should be changed frequently depending upon the nature of specimen and humidity.
14. In case of pressing deliquescent corolla or perianth, a layer of absorbent cleaning tissue is put over and beneath the flower before pressing. This tissue is peeled off after the specimen becomes dry.
Step # 3. Drying:
The essential thing is to dry the plant specimen as quickly as possible before the tissues have time to decay. It is therefore necessary to change the drying paper every day at least for the first few days. For this press may be put in the sun or near the gentle artificial heat, when the specimens are quite dry they are ready for poisoning.
Drying of specimens is carried out in two ways:
Drying of plant specimens without artificial heat:
It is followed universally and supposed to be most satisfactory. Plants are pressed in pressing papers between blotters. Corrugates are not used in this method. Plant press is locked for 24 hours. This is called ‘sweating period’. When sweating period is over, press is unlocked, blotters are removed and pressing papers are turned back. Now the specimens are rearranged as the situation demands.
Disadvantages in this method are:
1. Much longer time is needed for drying the specimens.
2. Blotters are to be changed at least 3 or 4 times during the entire process and wet ones are to be dried in the sun before using them again.
3. A large number of blotters are needed.
4. Less number of specimens can be processed per collector.
5. Specimens dried without artificial heat are liable to be infected by fungi because much time is taken in complete drying.
6. Larvae present within the flowers eat away some of the important parts.
7. Labour cost of drying per specimen is higher.
Drying of plant specimens with artificial heat:
It is much preferred by the collectors. The specimens are locked tightly within the field press for 24 hours. It is called ‘sweating period’. After the specimens have sweated, press is unlocked, specimens rearranged and put again in the drying press, locked with less pressure and are allowed to dry with the aid of artificial heat.
In this method corrugates are invariably used which provide air passage to the plant press for circulation of dry and heated air. For providing heat, gasoline stoves, kerosene lamps, coal fire, electric bulbs and hot steam pipes are used. Even large electric ovens may be taken into service and plant press is kept inside it at a suitable temperature.
Fernald (1945) has pointed out some disadvantages in drying of the specimens with the aid of artificial heat:
1. Plant specimens become brittle during drying.
2. Specimens loose their glaucescence or waxy bloom and colour.
3. Sometimes the specimens get permanently marked with the ridges of corrugates.
Step # 4. Poisoning:
Poisoning of the specimens should be done immediately after collection. Poisoning kills the plants and thereby prevent the formation of abscission layer and decay.
Generally used poisoning chemicals are mercuric chloride, lauryl pentachlorophenate (LPCP), formalin and the fumigates (volatile poisonous liquids) like methylbromide, carbon disulphide or carbon tetrachloride, paradichlorobenzene (PDB) etc.
Step # 5. Mounting:
When the specimen as well pressed, dried and poisoned, it is affixed with label on a mounting sheet (42 x 28 cm).
While mounting following precautions should be observed:
1. Mount only one specimen on one sheet.
2. Lower part of plant should be at the base of sheet.
3. Label should be pasted/printed on the right hand bottom of the sheet. Mounting is done either by glueing the specimen on sheet or by stitching.
Step # 6. Labelling:
After mounting the specimen, herbarium sheet is given a final touch by pasting a label at its lower right hand corner. The label is of the size 11 x 7 cm but its size may vary by 1.2 cm on either side. Some herbarium prefer to get the label printed on sheets.
A label must provide the following information:
Step # 7. Storing:
When specimens are ready in all respect, these are stored in wooden or steel almirahs for safe deposit and future record. These almirahs are essentially designed with two to three tiers of pigeon holes. The specimens are arranged in almirahs according to any internationally recognised system of plant classification after identification.
Each species is kept in a folded species cover which is lighter in weight and smaller in dimension than genus cover. Many species of a genus are kept together in a genus cover. The genus cover usually has the name of genus written or printed over it.
After identification the specimen should be incorporated (filed) in the herbarium.