Preparing Herbarium Specimens of Vascular Plants

!t ¿ PREPARING HERBARIUM SPECIMENS OF VASCULAR PLANTS rchC:,, ; "■■") NOy s i97] Agriculture/nformation bulletin No. 348,. '^'^"'^'^'^'f S£R|';¡L u¿QQr¡J¿^^^ ^\ Agricultural Research Service 1^ UNHIEir STATES DEPARÎMENT 0F AGRICULTURE ;, 336021 ACKNOWLEDGMENTS Without the help and suggestions of my many colleagues in systematic botany, this paper could not have been produced. I particularly wish to thank Harold St. John and F, A. McClure for advise on the preparation of plant specimens in their specialties. The staffs of the U.S. National Arboretum and the U.S. National Herbarium have offered much kind advice for which I am grateful. II CONTENTS Page Short guide to preparing an herbarium specimen IV The herbarium specimen and its preparation 1 The herbarium specimen _ 1 Preparing an effective herbarium specimen ._. 2 Collecting the specimen „ 3 Recording the data 6 Pressing the specimen 9 Drying the specimen . __ 11 Pressing problem plants 13 Special methods for preparing hard-to-press herbarium specimens 15 Wet collecting for field use - _. 15 Preserving fluids used 15 Equipment needed 17 Suggested techniques for preparing hard-to-prepare herbarium specimens 18 Floating or submerged aquatic plants „. 18 Plants with large parts ,—^ - --.^ - 19 Succulent xerophytes -.... - _ 20 Succulent mesophytes and hydrophytes 22 Plants with deliquescent or fragile flowers - 23 Plants of the pineapple family - - - 23 Plants of the palm family _„._ 24 Bamboo plants - ^ - 24 Screwpines - 25 Arborescent plants - 25 Selected references — 26 Appendix I --- 27 General guide to features to be illustrated by prepared specimens.. 27 Appendix II „ - - - - — 29 Plants with unisexual flowers —- -,- -^ ^ - - 29 wr I,- ^ TKn Issued September 1971 Washington, D.C. ^ —^s-^-n — — ■ ■ For aale by the Superintendent of Documents, U.S. Government Printing Office, Washington. D.C. 2Û4Û2 - Price 40 cents III Short Guide to Preparing an Herbarium Specimen A. Assemble the equipment. 1. Prepare the press with folds of newspapers to receive the specimens. 2. Gather tools and supplies: cut- ting tools, digging tool, notebook, piastic bags to hold unpressed specimens, and a camera to record dîfficult-to- describe plant parts. B. Collect the specimen and record the data. i. Survey the plants to be collected to find the most representative specimens. 2. Cut or dig the selected plant parts. 3. Make detailed notes of observa- tions that may be forgotten. 4. Place the specimens In a con- tainer for transport or in the press, if notes are made and separate parts collected, give the same identifying number to portions so they can be asso- ciated later. Prepare the specimen for pressing. 1. Place specimen in numbered newspaper fold. 2. Cut away excess parts, arrange leaves and flowers. 3. Write notes beside number in notebook; describe area, habit of plant, colors that may change, odors, and any special details* 4. Place fold between driers (ad- sorbent blotting paper) and corrugates (corrugated cardboard with channels running the width of the 12- by 17-inch piece) or heavy pads of newspaper. IV D. Press the specimen. I. Press the specimen witii its driers and corrugates tightly between press frannes or weight heavily beneath board or bool<s. E. Dry the specimen. L Change driers or newspaper pads in 24 hours and thereafter as they become moist. Do not disturb the specimens in the newspaper folds. 2. When dry to the touch, test for incompletely dried specimens (incompletely dried specimens will feel cooler and ends will droop when lifted from the fold). F. Store the specimen. 1. Store dried specimens in their folds tied between corrugates or mount on stiff 12- by 16-inch paper with bookbinder's Hol- land tape strips, casein, or plastic glue. 2. Label all specimens before storage or mounting. 3. Store only in insect-reststant furniture. Additional, detailed information on preparing herbarium specimens can be found in the rest of this bulletin. Trade names are used in this publication solely for the purpose of providing specific information. Mention of a trade name does not constitute a guarantee or warranty of the product by the U.S. Department of Agricul- ture or an endorsement by the Department over other products not mentioned. VI :^ PREPARING HERBARIUM SPECIMENS OF VASCULAR PLANTS^ By C. EARLE SMITH, TT 6ofontst, formerly, Plant Science Research Division, A^cultural Research Service, Beltsville, Md. THE HERBARIUM SPECIMEN AND ITS PREPARATION The correct methods of preparing plant speci- representing a living plant (fig. 1). For most mens for the herbarium are as many and purposes, an identifiable specimen can be de- varied as the correct methods of baking a cake. fined as one with either flowers or fruits, or both, Every practicioner finds a convenient method because most botanical literature discusses the that he will defend against all intruders. The differences in kinds of plants in terms of truly correct method of preparing herbarium reproductive structures. This is generally true specimens is that which produces the most for all groups of plants including the seaweeds, representative dried sample in the shortest mushrooms, mosses, and ferns, as well as the seed-bearing plants. Speciments of ferns and possible time. seed-bearing plants tend to be more bulky and difficult to prepare so this bulletin will be con- The Herbarium Specimen cerned with these plants. These, in fact, are the The most important element in botanical "vascular plants" of the title, because they collecting is the permanent record produced, include in their structures a system of tubes which is a specimen or a suite of specimens for transport of liquid (the vascular system). \ BN-«74«7 FIGURE l.-Suite of specimens representing Gunnero. peltata PhU. AGRICULTURE INFORMATION BULLETIN NO. 348, U.S. DEPT. OF AGRICULTURE Plant specimens are kept in an herbarium of an herbarium specimen is to record the com- (collection of herbs, literally, although the term plexity that is a plant species. Botanists have is now used for any kind of dried plant collec- long known that words or illustrations cannot tion) . To facilitate the storage of specimens and replace an actual sample of a plant as a stand- to allow the greatest flexibility in exchanging ard for comparison. This is recognized in the or borrowing specimens, the herbaria of the codification of rules for plant nomenclature United States mount dried, pressed plants on where a type specimen is required as the base sheets of stiff paper measuring about IIV2 by for a plant name. The first collection that is 161/2 inches (28.7 by 41.7 cm.). Because there described as a new species becomes the type are a number of facts about a plant (height of specimen against which ail future identifica- tree, geographical place where the plant was tions of this species must be measured. Any growing, kind of area where the plant was scientist doing research involving living plants found, colors, and odors) that do not show in the should prepare an herbarium specimen for per- dried specimen, additional information is placed manent record in case further work based on on a label that is fastened to the lower right the same material is necessary or the original corner of the sheet of mounting paper. Many identification of the plant is questioned. When- plant specimens do not hold together well and ever samples of plants are submitted for any some have only a few flowers, so the botanist sort of analysis, a specimen of the plant from dissecting the flowers wishes to preserve the which the sample was prepared ought to be dissected parts. He places all loose parts in held as a record. Ever the amateur gardener folded packets glued to the mounting sheet. may find that dried, pressed specimens of some Sometimes the appearance of a plant defies of his plants may serve as valuable standards description and the collector saves much time of size and identity for new cultivars tried in by photographing the plant before specimens subsequent growing seasons. Anyone involved are taken. Such photographs are usually fas- in the breeding of plants should preserve repre- tened to the mounting sheet also. sentative specimens as a check for the improve- Herbarium specimens are identified as accu- ment or regression of characters in progeny in rately as possible and are then filed in standard- the breeding program, A few minutes spent in size manila folders with closely related species. carefully preparing an herbarium specimen can These in turn are aggregated into groups of save much time if the exact identity of a par- closely related genera and into families. Most ticular plant must eventually be known or frequently, several manila folders are stored in recalled. a pigeonhole in the herbarium case according to the Engler and Prantl scheme of classifica- Preparing an Effective tion (16) ^ so that an individual genus or Herbarium Specimen species may be quickly recovered. (The Engler An efifective herbarium specimen not only is and Prantl classification attempts to group all identifiable and serves as a record of the species, plants in their natural relationship to one but also shows the range of variation of the another. This is the most widespread of several species in the place where the specimen origi- systems of classification.) The earlier herbar- nated. Although the standardization of the size ium specimens become the standards against of mounting paper in the herbaria of the United which later specimens are compared, and, thus, States has resulted in the universal exchage- the accuracy of the identifications is critical. ability and storability of specimens, it has The more complete the specimen and the more tended, at the same time, to bias the collector in detailed the notes on the label, the more accu- rate the identification can be.

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