a Southern Maryland Type Collection
Charcoal and Wood Reference Collection
creating a charcoal and wood reference collection, the first step
was to accumulate an identified collection of woods from trees
and shrubs at Jefferson Patterson Park and Museum in Calvert County,
Maryland and then convert them to charcoal. Twenty five of the
most commonly found hardwoods and softwoods are included in the
Southern Maryland Type Collection. Transverse, radial and tangential
surfaces of wood and charcoal are examined, as each type of wood
has a characteristic structure. The samples were organized by
scientific and common names and housed in specimen cabinets. Digital
images were acquired and posted on this website.
Plant Taxa are Covered?
are divided into two broad classes, usually referred to as "hardwoods"
and "softwoods." Softwood: The term softwood is a general term for trees that produce cones
(Gymnosperms), which usually have narrow, needle-shaped leaves
and are evergreen. The term originated as a description of the
hardness of the wood, although there are some hard softwoods like
Heart Pine (Yellow Pine Group, Pinus spp.). Hardwood: The term hardwood is a general term for flowering trees (Angiosperms)
that usually have broad leaves that are shed (deciduous) and produce
fruits. The term originated as a description of the hardness of
the wood, although there are some soft hardwoods like Balsa (Ochroma
spp.). Most imported tropical woods are hardwoods.
Methods Were Used to Create the Type Collection?
of dry, dead wood were extracted from branches or trunks of botanically
identified trees, shrubs and vines on JPPM property. Samples were
cut to manageable lengths (3 – 5 feet), bundled with bailing
wire and labeled with Tyvec sheets attached. Samples were stored
on outside, covered racks at the MAC Lab. Additional wood from
taxa not on JPPM property was either collected off-site or procured
from local hardwood dealers.
the reference wood collection (JPPMw), samples previously purchased
from Colonial Hardwoods were verified microscopically, labeled
and accessioned. Additional samples were donated by Alden from
the International Wood Collectors Society (IWCS), verified microscopically,
labeled and accessioned. Samples that were collected on the property
were used exclusively for charcoal, unless they were non-commercial
woods, shrubs or vines. The latter samples were cut to size (approx.
6” x 4’ x 1”), labeled and accessioned.
were trimmed to expose the radial, tangential and transverse surfaces.
For each of these planes, thin (15-20µ) sections were removed
by hand with a single-edge razor blade. The sections were mounted
on labeled microscope slides in a 1:1 solution of ethanol and
glycerin. Slides were heated briefly on a hot plate, to drive
off air bubbles and then examined under a compound microscope.
Digital images were acquired and stored on a computer.
of wood from the reference list were split into stake-size pieces
for carbonization. They were placed over hot coals in BBQ grills
with air tight lids and allowed to burn until about 80% consumed.
At this point, the lids were placed on and all vents closed. The
ovens were opened the next day and the wood that was reduced to
charcoal was placed in labeled, ziplock bags. The taxa were accessioned
into the charcoal collection (JPPMc) and placed in the reference
cabinet. Samples were arranged alphabetically by scientific name.
were broken by hand, exposing the transverse surface first, then
the tangential and radial faces secondly, if possible. Broken
surface were examined under an optical microscope, specifically
a dissecting type microscope that magnifies to about 300X with
good resolution. Parts of the sample-fragments with the largest
surfaces were placed on a dish containing sand. Sand is used to
allow accurate manipulation of the charcoal fragments. The sand
is slightly moistened with glycerin to increase cohesion of sand
grains and decrease the adhesion of the fragment to the sand-mass.
Digital images were acquired and stored on a computer. After identification,
sub-samples were returned to their bags and cataloged alphabetically
by scientific name in a specimen cabinet.
most efficient way to identify charcoal is by examining freshly
fractured surfaces (end-grain, radial and tangential) using reflected
light. Wood samples were identified prior to carbonization using
memory, experience and standard microscopical wood keys and descriptions
(Kukachka, 1960 for softwoods; Panshin & DeZeeuw, 1980 for
hardwoods). Trade or common names are from Little (1979). Species
designations were deduced using present tree distributions and
range maps (Alden, 1995 & 1997; Elias, 1980, Gleason &
Cronsquist, 1963; Little, 1979).
(Levels of Determination)
wood & charcoal identification from archaeological contexts
has limitations not always apparent to researchers. These limitations
are based on many factors, including the size of the sample, the
level that one looks at the sample (i.e. microscopic) and the
evolutionary conservative nature of wood & charcoal with respect
to species determination.
hierarchy of plants is based on a taxonomic system developed by
Carl Linnaeus (1707-1778), where each specific type of plant is
given a binomial (“two-names”) the genus (like our
family names, e.g. Smith) and a species name (like our first names,
e.g. John). The Linnaean binomial is the preferred term used when
conversing about wood, unless a well accepted trade name (the
most typical “common name”) is assumed. The binomial
is italicized, with the genus first and the species epithet second
(e.g. Eastern White Pine is Pinus strobus). When one refers to
an unknown species the term “sp.” is used and when
one is referring to more than one species in a genus, the plural
“spp.” is used. Similar genera are grouped into Families
(ending in –aceae), similar families into Orders, similar
orders into Classes, and similar classes into Divisions. Some
individual species of plants, trees or woods can have numerous
common names, while a particular common name can have numerous
species associated with it. On this website, the binomial name
is given, as well as accepted common names.
people think of types of wood, they generally are thinking in
terms Pine, Oak, Maple, Spruce, etc., which describe genera of
trees (Pinus, Quercus, Acer and Picea, respectively). Even with
small samples, identification of wood & charcoal to the genus
level is usually very accurate.
of Species Groups
groups are groups of species, within a genus, that have anatomical
similarity. For instance, the Pines (Pinus spp.) can be grouped
into the Red Pine Group, White Pine Group and Yellow Pine Group.
The Oaks (Quercus spp.) contain the Red (Erythrobalanus) and White
(Leucobalanus) Groups and the Maples (Acer spp.) have species
that separate into the Hard and Soft Groups.
microscopic determination of wood & charcoal to the species
level is usually not possible. These limitations are based on
the evolutionary conservative nature of wood. Species of wood
(trees, and plants in general) have been determined in the past
from the number, size, shape and orientation of external features,
such as reproductive structures (flowers, fruits, cones), foliar
structures (leaves or needles) or other parts of the plant like
bark or branch morphology. These characters are rarely present
in objects made of wood & charcoal. Current, molecular techniques
of DNA analysis are moot because of the paucity or lack of DNA
in heartwood and the contamination of archaeological wood by fungi
types of wood were burned (branches, roots, and shrubs in addition
to commercial species). There are no keys for charcoal identification
or for woody branches. There are no comprehensive keys for non-commercial
trees and shrubs. Wood samples that have been turned to charcoal
have lost characteristics important for accurate identification.
There are no differences with respect to weight, density, hardness
or color once wood has been charred. Cellular characters are more
difficult to discern using reflected light microscopy and the
material has lost most color contrast in comparison to wood examined
with a compound microscope. Sample sizes of charcoal from archaeological
contexts are usually smaller than wood samples from industrial
contexts. Most identification keys are based on large samples
from commercially important trees. Identification of samples is
tenuous when samples are smaller than 2-4 mm on a side. At this
scale, a sample of white oak group may appear to be chestnut.