Botany - B.E. Yakubenko 2017

Part Three. Kingdom Plantae
Chapter IX. Division Angiosperms, or Flowering Plants (Angiospermae, Magnoliophyta)
Laboratory Practical Session Topic 14.43. Methods of Herbarium Preparation

General Remarks. A crucial stage in mastering a botany course is studying The Diversity of Ukraine's vegetation. To this end, it is practical to examine both live plants and herbarium specimens. Gathering a proper herbarium requires mastering the techniques of plant collection and preservation. Preparation for this process must be thorough, with a clear understanding and division of the work into three distinct stages: preparatory, field, and laboratory.

In the field, you must carefully select representative species both for inclusion in the herbarium and separately for identification. If you want to create a high-quality herbarium, make sure that the excavated plants, freed from soil, are placed between drying sheets directly in the field. At the same time, include fully completed labels.

In the laboratory, conduct morphological analysis and plant identification with utmost care. Whenever possible, cross-check your identifications with atlases, keys, or slides. Another essential requirement is the neat and complete filling out of labels, plant lists, and the assembly of the final herbarium.

Objects: representatives of plant species from various families.

Tasks:

1. Prepare 120 herbarium sheets (42x56 cm), 120 labels (12x8 cm), a press, twine, a folder, and other accessories for plant preservation.

2. Collect live plants for herbarium mounting and identification.

3. Master the methodology of plant morphological analysis.

4. Acquire the techniques of plant identification.

5. Compile a list of the collected plants (using both Latin and Ukrainian names).

6. Prepare the collected plants in their final, mounted form.

Equipment and Materials: an excursion folder (45x32 cm); 200–300 sheets of drying paper (newspaper or wrapping paper); ready-made or homemade herbarium presses (45x32 cm); cord, twine, or other binding material (3 m); 120 herbarium folders (folded 42x56 cm sheets for mounting specimens); 120 labels (12x8 cm); a cardboard folder (45x32 cm) for mounting the herbarium; a pocket or utility knife for digging up plants; a magnifying Glass, forceps, dissecting needles; a notebook or notepad; a booklet of field labels; plastic bags (or cheesecloth ones), and small pouches.

METHODOLOGICAL GUIDELINES FOR Plant Pressing and Herbarium Preparation. A herbarium (derived from the Latin word herba, meaning grass) is a collection of dried, identified, and properly labeled plants. A systematic herbarium includes characteristic plant species from forests, bogs, fields, forest plantations, natural forage lands, slopes, outcrops, shelterbelts, fallow lands, etc. A student's specific herbarium—whether in forestry, landscape gardening, agronomy, fisheries, plant protection, ecology, biotechnology, or other fields—should include plant species that reflect the professional training of a future specialist.

It is best to collect plants during their flowering period, and some during fruiting. You should gather typical specimens featuring a ROOT system, a well-defined stem, branches, leaves, inflorescence, and a flower.

Plant collection should ideally begin in spring and continue throughout the growing season. Keep in mind that certain plants (such as corydalis) bloom very early in spring. These are ephemerals that quickly complete their vegetation cycle and will no longer be suitable for pressing by the time practical training starts. The optimal period for gathering plants is late May through June. Plants should be collected in clear weather after the dew has evaporated. Specimens gathered after rain or in the early morning (while still wet with dew) dry poorly or turn black during the drying process. For excavated specimens, the underground parts must be thoroughly cleaned of soil. Select plants of typical size for the species: small ones should be collected in quantities of 3–5, while large ones must be folded once or twice when placed in the drying paper. When a plant is exceptionally large and folding is impractical, collect only characteristic parts—SHOOT segments with leaves, a flowering shoot with an inflorescence, flowers, etc. For the identification of certain plants, it is mandatory to have, alongside flowers, at least immature fruits (e.g., plants from the sedge, aster, legume, and umbellifer families, among others). Collected plants are placed fresh and unwithered into a folder with drying paper, carefully straightening them out while inserting a working label indicating the Location, habitat conditions, date, and collector's name. Overlapping parts should preferably be separated by strips of drying paper. Before drying, specimens with thick roots, rhizomes, bulbs, or succulent parts should be sliced, drying only the halves. In some cases, fleshy, succulent Organs (or the entire plant) must be briefly dipped in boiling Water, which accelerates drying and preserves their natural color. Flower coloration is best retained by packing the perianth parts with bits of cotton wool or filter paper. The paper containing the plants should be interleaved with 1–3 sheets of dry paper (depending on plant thickness) for drying, ensuring the stack remains uniform in thickness. The plant folder is then placed in a herbarium press or between two sheets of plywood, tightly bound with cord, or weighted down with 4–8 bricks on top. The pressed specimens are then hung up and kept in a well-ventilated room.

During the first two days of drying, change the paper three times a day, and thereafter once a day. The damp paper removed from the plants should be spread out or hung up to dry.

As a rule, plant drying takes 3–5 days. The dried specimens (each species separately) are placed inside mounting paper. There is no need to sew or glue the plants to it. Each mounting sheet, alongside the dried specimen, must feature a standard-sized and properly formatted label indicating: 1) the Latin and Ukrainian names of the family; 2) the Latin and Ukrainian names of the species; 3) habitat conditions (e.g., cornfield, wheat crops, pine forest, oak forest, dry meadows, forest bogs, etc.); 4) the geographical location of collection—region, district, village, forestry enterprise; 5) economic significance and indicator properties; 6) collection date; 7) name of the collector.

The label is placed within the herbarium framework during the systematic Organization of all collected materials and their final assembly. The herbarium is placed inside a cover folder marked with: 1) the student's surname and initials; 2) faculty; 3) year and academic group; 4) academic year; 5) number of collected species. A list of the preserved plants must also be attached to the herbarium.

When submitting the herbarium, the student must be well-versed in the Latin name of each plant, its family, habitat details, economic importance, and flowering time.

The morphological section of the herbarium includes material illustrating the external (morphological) Structure OF THE shoot, stem, root, leaf, flower, inflorescences, and fruits. Specifically, students must demonstrate—using self-collected material—shoot structure, internode development types, growth patterns, branching, as well as the principal underground and aerial metamorphisms.

The herbarium materials on root Morphology must showcase various types of roots and root systems according to their shape, origin, and most common modifications. Materials on leaf morphology should feature key types of simple leaves (by blade shape, dissection, margin shape, venation, etc.) and compound leaves. The primary leaf metamorphoses must also be demonstrated.

The morphological herbarium should illustrate The structure of various types of flowers (with double and simple perianths, polypetalous, gamopetalous, superior Ovary, etc.) and inflorescences (determinate, indeterminate, simple, compound, etc.). Finally, the morphological section must illustrate all Major Types of dry and fleshy fruits and multiple fruits.

Although the morphological herbarium is an independent section, it is mounted According to the principles of a systematic herbarium regarding paper size, labeling, etc. However, unlike a systematic herbarium, all its materials are sewn onto separate sheets of paper according to relevant themes (e.g., dry fruits, compound leaves, etc.).

Specific features of Aquatic Plant Pressing. Collecting and properly drying plants during botanical research conducted in water bodies is an essential area of work. It often receives insufficient attention, resulting in unattractive specimens that are impossible to identify.

The collection and drying of aquatic plants differ from terrestrial ones and possess unique characteristics. The plants are dried in the same manner as terrestrial ones—between sheets of newspaper within botanical presses.

To obtain optimal herbarium specimens of aquatic plants, pressing and drying must be carried out meticulously. Whenever possible, the herbarium should include all PARTS OF THE plants: The Root System, stems and their modifications, leaves, inflorescences and flowers, fruits, and seeds.

Submerged plants and floating-leaved plants with thin rhizomes or lacking roots are collected using aquatic rakes, dredges in deep waters, and bottom grabs on the seabed or lake floor. Plants are uprooted along with their root systems only in soft muddy sediments. Plants with thick rhizomes are cut using a sickle knife.

Afterward, the plants are washed free of mud (in a bucket or from the side of a boat) and, before being placed in herbarium folders, they are either put into polyethylene bags (several bags of various sizes should be available) or wrapped in damp gauze pads (measuring 30x30 cm) and then placed into polyethylene bags. The bags containing the plants are packed tightly into a bag, where they remain until returning to the dormitory or home.

Placing most aquatic plants directly into a field press folder, as is done with terrestrial plants, is discouraged, as plants in such folders tend to dry out too quickly, leading to deformed leaves and flowers. Plants placed in gauze pads (especially species with dissected foliage) release excess surface moisture, can remain fresh for several days, and decompose more easily compared to those kept in polyethylene bags.

Plants with aerial stems and leaves that rise above the water surface, typically growing in shallow waters (such as arrowhead, bur-reed, flowering rush, etc.), are dug up using knives, spades, digging tools, or pulled out by hand. Harvesting taller plants (such as reeds, cattails, and bulrushes), which possess thick, resilient, and long rhizomes deep in the substrate, is more challenging. Therefore, such plants are placed into herbarium folders without their subterranean parts, but necessarily including Generative organs.

Broad-leaved pondweeds, hornworts, bladderworts, water milfoils, and other plants with finely dissected leaves dry without complications. If the specimens are dense and large, they are interleaved with sheets of newspaper. The damp newsprint must be changed twice a day. To do this, a dry, unfolded folder is placed on top of the opened folder containing the plant; then, holding both the upper and lower folders firmly with both hands, they are flipped over, and the wet one is removed.

Plants with delicately dissected leaves (such as bladderworts, hornworts, water milfoils) and other submerged species whose stems and leaves are covered with Algae must be transferred to fresh drying paper during the first paper change while the plants are still damp; otherwise, these plants will become irreversibly fused to the paper. This process must be monitored closely and performed in a timely manner.

Particularly thin and delicate plants are first floated and arranged in a basin of water, after which a sheet of paper is slid underneath them. The paper is then carefully lifted out of the water along with the plant, ensuring the specimen is not washed away, and dried while resting on these sheets inside folders within the press in the standard manner.

Large plants with thick, fleshy rhizomes and large, thick leaves (sometimes exceeding the width of a herbarium sheet, such as water lilies and yellow water lilies) cannot be mounted whole in the herbarium. Instead, collectors take several leaves with petioles, flowers, fruits, and the basal rosette of leaves with a portion of the rhizome. The rhizome and leaf rosette are split lengthwise, spread open, and placed into folders in this state, with the fleshy interior carved out of the rhizome. If the leaf rosette is too large, only one half is taken.

Floating leaves, flowers, and rosettes with delicate submersed leaves are placed into separate paper folders labeled to indicate which plant they belong to. Thick floating leaves typically undergo significant deformation and lose their shape during drying. To retain a record of the leaf's true shape and size, we recommend tracing its outline on a white paper sheet, inserting this template into the folder alongside the leaf, and storing it with the herbarium specimen. When pressing rosettes of delicate submersed leaves, they should be interleaved with parchment or tracing paper. On top of the leaves, flush with the thick Base of the rosette and rhizome, a layer of folded paper sheets is placed and changed regularly during the drying process. The spacers between individual submersed leaves should not be removed until drying is complete, and they do not need to be transferred to fresh paper. Herbarium presses containing such plants should ideally be left in the press under pressure for several hours, which helps minimize the deformation of fleshy floating leaves.

Researchers collecting plants for a herbarium should be aware that many species of aquatic plants are listed in the Red Data Book of Ukraine and are protected by law. Before starting fieldwork, one must review the lists of protected plant species in the regions where research is being conducted.