Chapter 3 The Gross Features of Wood
木材宏观特征
Ⅰ. The nature of gross features
木材宏观特征的属性
Ⅱ. The gross structural features of wood valuable in identification
具有木材识别价值的宏观结构特征
Ⅲ. The physical properties of wood valuable in identification
具有木材识别价值的物理性能
Ⅳ. Principles of wood identification
木材识别原理
Ⅰ. The nature of gross features
In wood identification of gross level, we often need to
use lots of gross features of wood, so it necessary for us
to know well some basic features of wood.
The gross features of wood are of two kinds:
— Structural features
those traceable to wood structure
e.g.: wood rays, pores, annual rings
— physical features
those no relation to structure
e.g.: color, odor, weight
Ⅱ. The gross structural features of wood
1. The three standard planes of wood
In wood anatomical research, all the wood structural features
are discussed on this three standard planes.
• Cross Section：cut at right angles to the grain (axis) .
• Tangential Section：cut along the grain and right to wood rays
• Radial Section：cut along the grain and following a radius
2. Growth increments（生长轮）
In most species in temperate climates, the difference
between wood that is formed early in a growing season and
that formed later is sufficient to produce well-marked annual
growth rings. The age of a tree at the stump or the age at any
cross section of the trunk may be determined by counting
these rings.
2-1 Annual rings of normal type (正常年轮)
• Conceptions of growth increments and annual rings
The former is the layer of wood produced in one growth season,
and the latter is the layer of wood produced in one year.
In cold and temperate areas, there is only one growing season in a
year, so in this case, growth increments and annual rings are the same
thing; while in tropical and some subtropical areas, there are more
than one growing season in a year, and in this case, growth increments
and annual rings are two different conceptions.
• The appearance of annual rings on different planes
Concentric rings
Parallel strips
Parabolas mounted
one after another
2-2 Earlywood and latewood (早材与晚材)
• Earlywood
The inner part of the growth ring formed first
in the growing season is called earlywood (spring
wood). Earlywood is characterized by cells with
relatively large cavities and thin walls.
• Latewood
The outer part of the growth ring formed later
in the growing season is called latewood
(summer wood). Latewood cells have smaller
cavities and thicker walls.
2-3 Annual rings of abnormal type (非正常年轮)
• Discontinuous rings
It is the ring which was interrupted at one or more points because
that the growth of the tree was stopped at local places by fire or
insects attack, while the growth of other parts of the tree continued
normally.
• False rings
The tree growth in diameter may be interrupted by the influence
of drought or defoliation because of insect attack. When the
influence was over, the tree growth continued again, and so, more
than one ring was formed in the same season. In such an event, the
inner rings usually do not have sharply defined boundaries and are
termed false rings.
• Identification of false rings
False rings can be distinguished from true rings in that the cells
composing the false summerwood grade gradually, not only to the
inside but also to the outside.
2-4 Annual rings in relation to quality of wood
The quality of wood is affected by ring width in most and
probably in all tree-species.
Generally speaking, rings of unusual width frequently
mean lumber of inferior quality, while lumber with narrow
rings usually means high mechanical strength and high
quality.
For the same tree species, the faster a tree grows, the
wider the annual rings, and the lower the quality of wood
produced.
3. Sapwood and heartwood（边材与心材）
3-1 Conception of sapwood and heartwood
Sapwood
Heartwood
3-2 Formation of heartwood
Heartwood arises from sapwood. When a tree is young,
all the section of the tree stem was used to conduct sap,
so that all wood belongs to sapwood.
As the tree grows on, the tree stem becomes thicker
and thicker, and part of the stem near the pith is not
needed to play conduction function anymore. At this
time, some kinds of extractives would deposit in the
area that had no conduction function, and gradually
this part of the stem turns into heartwood.
As the tree grows older and older, more and more
heartwood would be produced in this way.
3-3 Main differences of heartwood from sapwood
Compared with sapwood, usually heartwood exhibits
significant difference in the following 7 aspects:
• color is darker;
• infiltration content is higher;
• weight is heavier;
• strength is higher;
• natural durability is better;
• permeability is lower;
• moisture content of green wood is much lower.
3-4 Some conceptions
• Heartwood species(心材树种）：The wood species that possess
significant difference between sapwood and heartwood in color.
• Sapwood species(边材树种）：The wood species that possess
no significant difference in color and moisture content between
the two parts near pith and bark.
• Heartwood concealed species(隐心材树种）：No difference in
color but with difference in M.C. between sapwood and
heartwood.
• False heartwood(假心材）：pathologically darkened wood
near the center in sapwood species.
• Included sapwood(内含边材）：fungus affected light colored
wood occurred in heartwood of heartwood species.
4. Wood rays（木射线）
4-1 Conception
The ribbon-like tissues extending in the
radial direction, i.e., from the pith toward
the bark running at more or less right angles
to the growth increments, when viewed on
the transverse section.
4-2 The textile structure of wood
In structure, wood bears some analogy to
a textile in which the threads run at right
angles.
In this analogy the rays would represent
the cross threads, and the remaining tissues
the long threads.
4-3 Functions of wood rays
— Radial conduction;
— Storage of nutrients;
— Strengthening in transverse.
4-4 Appearances of wood rays on different planes
C: rays from pith to bark;
R: flecks or ribbons at right angles to the grain;
T: staggered small lines along the grain.
5. Wood parenchyma (木薄壁组织)
5-1 Ray parenchyma （射线薄壁组织）:
the main body of wood rays.
5-2 Epithelial parenchyma （伴生薄壁组织）:
the secretory cells composing resin canals and gum canals.
5-3 Longitudinal parenchyma （轴向薄壁组织）:
the parenchymatous cells extending along the grain in the
form of strands.
5-4 Distribution of longitudinal parenchyma
The distribution patterns of longitudinal parenchyma can be
divided into two groups:
— Apotracheal parenchyma （离管型薄壁组织）：
Diffuse parenchyma （星散型）
Diffuse-in-aggregate （星散聚合型）
Apotracheal banded （离管带状）
Initial
（轮始型）
Terminal
（轮末型）
— Paratracheal parenchyma（傍管型薄壁组织）
Scanty parenchyma （稀疏傍管）
One-sided
（单侧傍管）
Vasicentric
（环管型）
Aliform
（翼状）
Confluent aliform
（聚翼状）
Paratracheal banded （傍管带状）
6. Pores (管孔）
6-1 Definition
Pores are the bird-eye views of vessel elements.
6-2 Main difference between softwood and hardwood
• Softwood — Nonporous wood
without pores, except Ephedraceae（麻黄科）
• Hardwood — Porous wood
with pores, except Tetracentron sinensis（水青树）
6-3 Arrangement of pores（管孔的排
列）
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Ring-porous wood — 环孔材
Diffuse-porous wood — 散孔材
Semi-porous wood — 半环孔材
Radiant porous wood — 辐射孔材
Tangent porous wood — 切线孔材
Staggered porous wood —交叉孔材
6-4 Distribution of pores（管孔的分布）
Usually refers to the pores in latewood of ring-porous wood.
Flame-shaped
火焰状
Scattered star-like
星散型
tangent line –like
弦切型
6-5 Combination of pores（管孔的组合）
Usually refers to the relationships between pores.
— Solitary pores / 单管孔
— Compound pores / 复管孔
— Pore chains / 管孔链
— Clustered pores / 管孔团
7. Resin canals（树脂道）
7-1 Normal resin canals
 Structure
 Function: Storage room of resin
 Wood species with normal resin canals (Pinaceae)
Pinus (松属)；Picea(云杉属)；Cathaya(银杉属)；Larix(落叶松属)
Pseudotsuga(黄杉属)；Ketereeria(油杉属) —无径向树脂道
7-2 Traumatic resin canals
 Formation: They are formed only when the tree was injured
 Appearance: Lager and connected in tangential direction
 Distribution: They occur only in the ring that suffered injury
8. Texture and grain （结构与纹理）
8-1 Texture
• Definition:
Texture is concerned with the size of wood cells and degree of
difference in size of cells.
• Terms of wood texture
Fine textured, Coarse textured
Even textured, Uneven textured
Smooth textured, Harsh textured
8-2 Grain
• Definition:
Grain refers to the longitudinal alignment of wood cells.
• Terms of wood grain
Straight grain, Diagonal grain, Spiral grain, interlocked grain,
cross grain（斜纹）
9. Figure in wood （木材花纹）
9-1 Definition:
In a general sense, any distinctive markings of wood may be
described as figure. Commercially, the term figure is
restricted to the highly decorative patterns.
9-2 All kinds of wood figure
Ⅲ. The physical properties of wood
1.
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Color
Formation: Extractives; Fungi attack; Chemicals; Dyes
Variation: Sapwood and heartwood; Weathering; Aging
Practical value:
Asset: as in Hongmu, the dark the color of the wood, the higher the value.
Liability: as in surface decoration, dark color should be avoided.
Wood identification: color is used as a supplementary feature.
2. Luster
• Definition:
Luster is the property of wood that enables it to reflect light, in other words,
the property of exhibiting sheen.
• Variation: Structure of wood; Infiltrated products; Section plane;
Incident light angles; Aging
• Practical value:
Wood quality evaluation: lustrous → sound
Wood identification: used as supplementary features, e.g., catalpa-sassafras
3. Odor and taste（气味和滋味）
• Odor: tested with nose
At ordinary temperatures, wood substance itself has no
scent; i.e., it does not emit free molecules into the air. When an
odor is present, it is due to substances deposited in the wood
(infiltration products) or formed through the action of fungi or
microorganisms.
The odor from the former is favorable: cupress, sandalwood.
The odor from the latter is unfavorable: it means decay.
• Taste: tested with tongue
The taste of wood mainly comes from the extractives, and can
be used as a supplementary feature in wood identification.
Wood with unfavorable taste is avoided in wooden container of
comestible products.
4. Weight（重量）
• Value in wood identification
particularly when the discrepancy between species under
comparison is unusually great.
• Grades of wood weight
light: d < 0.3; middle: d = 0.3~0.5; heavy: d> 0.5
• To wood quality, the heavier the wood, the better of the wood.
Standards of Hongmu: d > 0.8
Guajacum （绿檀）：d=1.3
Hsiemu（蚬木）：d=1.0
Balsa wood（轻木）：d=0.12
5. Hardness
• The relative hardness or softness of wood is a useful indicator
of its physical properties.
• A useful idea of the approximate hardness of wood can be
gained by testing it with a knife or the thumbnail.
Ⅳ Principles of Wood identification
1. Bi-search key — 对分检索表法
表 3-3 六种紫檀属红木对分检索表
1. 木射线主为单列，偶见多列 .........................................................................................................2
1. 木射线主为多列（2 列）
，单列较少 ..............................................................................刺猬紫檀
2. 散孔材，半环孔材倾向可见或明显..........................................................................................3
2. 散孔材 ...........................................................................................................................檀香紫檀
3. 新切面有香气或香气浓郁 .............................................................................................................4
3. 新切面无香气 ...................................................................................................................囊状紫檀
4. 木刨花或木屑冷水浸出液为红色 .............................................................................................5
4. 木刨花或木屑冷水浸出液蓝绿色荧光很明显............................................................鸟足紫檀
5. 轴向薄壁组织主为傍管细线状，稀少翼状及环管状....................................................越柬紫檀
5. 轴向薄壁组织主为傍管带状、聚翼状或者细线状及环管状........................................大果紫檀
2. Perforation cards — 穿孔卡片法
3. Wood identification with computer — 木材计算机识别
Reflection and practice:
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How to generate the cross, radial and tangential sections on a log?
The difference between annual rings and growth increments?
Appearance of annual rings on cross, radial and tangential sections?
How to distinguish false ring from true ring?
How does the heartwood form in a tree?
Main differences between sapwood and heartwood?
Functions of wood rays in a living tree?
Appearance of wood rays on cross, radial and tangential sections?
How many kinds of parenchyma are there in wood, their names and functions?
The most significant difference between softwoods and hardwoods?
What is pores in the field of wood structure?
Distribution patterns of pores in ring porous, semi-ring porous, and diffuse
porous woods?
Structure of resin canals?
Name the six genera of softwood species that have normal resin canals in China
in Latin and Chinese.