Biermann Ch. Handbook of Pulping and Papermaking

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Table 26-1. Dichotomous hand lens key of major

Wood with normal resin ducts 2

Wood without normal resin canals 8

Resin ducts numerous, evenly distributed

in outer portion of every ring; generally

visible to naked

eye,

easily seen with hand

lens;

resinous odor 3

Resin ducts sparse, unevenly distributed

and sometimes absent in some rings;

occasionally appear as 2-many in a tan-

gential row, barely visible to the naked

eye as light or dark flecks 5

Transition from early to late wood gradual;

wood soft, light, quite even in density; coarse

to medium textured

Pinus

lambertiana,

monticola

Transition from early to late wood abrupt;

wood medium hard to hard 4

Wood medium hard; resin canals con-

fined mostly to outer (latewood) portions

of growth rings

Pinus

ponderosa,

contorta

Wood often heavy and hard to cut; resin

ducts distributed throughout center and

outer portions of growth rings

Pinus

spp.

Transition from early to latewood gradual 6

Transition from early to latewood abrupt 7

6. Wood light pinkish yellow to pale

brown, often somewhat lustrous

Picea sitchensis

6. Wood yellowish to orange red; charac-

teristic odor

Pseudotsuga menziesii

Wood yellowish to orange red or deep red, not

oily, characteristic odor on fresh cut surface;

rings often wavy in slow growth; resin canals

often in tangential lines of 2-3

Pseudotsuga menziesii

Wood brownish cast, somewhat oily appear-

ance;

no characteristic odor; in slow growth,

ring contours generally smooth; resin canals in

groups of

2-5,

but not in tangential lines

Larix

occidentalis

8. Wood without distinct odor 9

8. Wood with distinct odor 12

9. Wood medium to coarse textured 10

9. Wood fine textured, dense, fairly heavy;

heartwood light orange to rose red

Tcaus brevifolia

10.

Wood whitish to pale brown some-

times with purplish tinge; gradual

transition from early to latewood;

medium textured

Tsuga

heterophylla;

Abies

spp.

10.

Wood red to deep reddish brown or

U.S. conunercial softwoods.

yellowish to dark reddish brown to almost

black; coarse textured; abrupt transition 11

11.

Wood light cherry red to deep reddish brown;

light

moderately lightweight; usually uniform

rate of growth

Sequoia sempervirens

11.

Wood variable in color, yellowish to light or

dark brown, reddish brown to almost black;

wood often greasy or oily; cuts like hard rubber

with knife; usually irregular rate of growth and

discontinuous growth rings

Taxodium distichum

12.

Wood with fragrant, "cedar-like" or

sweetish odor 13

12.

Wood with ill-scented, or with rancid

odor 17

13.

Wood reddish brown to dull brown 14

13.

Wood yellowish white to pale yellowish

brown 16

14.

Wood dull reddish to pinkish brown,

often with streaks of included sap-

wood; fine textured, moderately hard

and heavy; characteristic mild spicy

odor

Juniperus occidentalis

14.

Wood reddish brown to dull brown;

medium to coarse textured 15

15.

Wood sometimes with lavender

tinge;

Fre-

quently with pecky rot; texture within

growth rings even, cuts smoothly across

growth rings; distinct odor like pencils and

with distinct acrid taste

Libocedrus decurrens

15.

Texture with growth rings uneven, cuts

brashly across growth rings because

latewood considerably harder than early-

wood; never with pecky rot; sweet "cedar"

odor

Thuja plicata

16.

Wood yellowish white to pale yel-

lowish brown; distinct pungent,

ginger-like odor; medium to coarse

textured

Chamaecyparis lawsoniana

16.

Wood bright, clear yellow, darkens

upon exposure; odor resembles raw

potatoes; fine to medium texture

Chamaecyparis nootkatensis

17.

Wood yellowish white to pale brown; uni-

form rate of growth

Chamaecyparis lawsoniana

17.

Wood variable in color, yellowish to light

or dark brown, reddish brown to almost

black; irregular rate of growth

Taxodium distichum

MICROSCOPIC ANATOMY OF SOFTWOODS 545

Fig. 26-4. Sketch of Abies magnifica (r) show-

ing nodular end walls and indentures. Two

crystals also appear. From Kukachka (1960).

yellow cedar is unique in that it has homocellular

rays composed of either parenchyma or tracheids

and very few heterocellular rays. The low rays of

hard pines are often homocellular with tracheids.

Ray tracheids may be dentate, when tooth-

like projections on the horizontal walls are pres-

ent. In the spruces these are small and observed

in the latewood. Hard and red pines have dentate

ray tracheids, whereas soft pines have nondentate

ray tracheids. These are depicted in Fig. 26-3.

Ray parenchyma end walls may be smooth

(e.g., Thuja) or nodular with bead—like projec-

tions (e.g., Abies), In some species the corners of

the ray parenchyma are observed to have pit—like

depressions, called indentures, where the vertical

and horizontal walls meet. These features are

depicted in Fig. 26-4.

Ray cross—field pits

Cross—field pits occur between ray parenchy-

ma and longitudinal tracheids. Phillips (1948)

described five types of cross—field pits that are of

importance in identification of softwoods. Use

cross—fields of the first few earlywood tracheids

(if possible) of a growth ring as those of the

latewood tracheids vary in structure. Fenestriform

and pinoid pittings are easy to distinguish; the

Fig. 26-6. YtnesirifOYrxn^iiimginPinusstrobus

(top,

with a row of interspersed ray tracheids)

and P. monticola, approximately

600

latter generally occur with dentate ray tracheids,

although red pine has dentate ray tracheids with

fenestriform pitting. Piceoid, cupressoid, and

taxodioid (especially the latter two) are difficult to

discern since there is overlap between these types.

Hoadley, page 26, and Jane, page 95, have excel-

lent diagrams of

these.

Fig. 26-5 shows diagrams

of these pits.

Fig. 26-5. Cross-field pitting: piceoid (left), cupressoid (center), and taxodioid (right).

546 26. SOFTWOOD ANATOMY

Fenestriform pits are large, borderless rectan-

gular "window—like" pits with usually 1—2 pits

per cross—field (Fig. 26-6). Most other types

have 2 to 6 pits per cross—field. These distinctive

pits are characteristic of the soft (white, scotch,

etc.) and red pines. Sugar pine has 2—4

fenestriform pits per cross—field.

Pinoid are elliptical to irregular polygons in

shape (Fig. 26-7). They vary in size. The bor-

ders may or may not be visible around the aper-

tures.

When they are visible they are narrow and

usually wider on one side than the other. These

are characteristic of the hard pines (except red

pine) and occur in species with dentate ray

tracheids.

Piceoid have slit—like apertures that may

extend beyond the visible border (Fig. 26-8). The

width of the aperture is less than that of the

aperture to the border. They occur in spruce,

larch, and Douglas—fir.

Cupressoid are similar to piceoid, but the

apertures are contained within the boundaries of

the border and their width is slightly less than that

Fig. 26-7. Pinoid pitting in Pinus banksiana

(top,

with shallowly dentate ray tracheid) and

P. ponderosa (prominently dentate ray

tracheids), approximately 600x.

Fig. 26-8. Piceoid pitting in Picea sitchensis

(top,

note nodular end wall), Larix

occidentalism

and Pseudotsuga menziesii (note indentures),

approximately 600 x.

MICROSCOPIC ANATOMY OF SOFTWOODS 547

of the border on either side (Fig. 26-9). They

occur in most of the genera of Cupressaceae

(except in Thuja) and in Tsuga.

Taxodioid pits have a regular elHptical shape

with apertures that are larger than those of the

previous two types (Fig. 26-10). The aperture is

wider than the border on either side of the aper-

ture.

They occur in Sequoia, Taxodium, Thuja,

and Abies genera.

Number of intertracheid pits across

the

fiber

The intertracheid, bordered pitting of

tracheids pits (r) is usually uniseriate (generally

only one pit across the width of the tracheid,

although two may occur where tracheids overlap).

Sugar pine may have four consecutive pit pairs in

the first few fibers of the earlywood. In some

Pip g^;

species there are two or more columns of

pits

that

may be alternate or opposite. Opposite

multiseriate pitting occurs in Sequoia and

Taxodium (Fig. 26-11). Alternate multiseriate

pitting is characteristic of only Araucaria and

Agathis amongst all conifers. Intertracheid pitting

is usually confined to the radial surface, although

its presence on the tangential surface in the

latewood is common. The lack of intertracheid

pitting on the radial walls of the latewood of

southern

pines

is used to distinguish them from the

soft pines.

Fig. 26-9. Cupressoid pitting in Lihrocedrus

decurrens

(to^^

see nodular end walls), Juniper-

virginiana^

and

Taxus

brevifolia^

-600x.

Fig. 26-10. Taxodioid pitting in Abies concolor

(top,

note crystals in marginal parenchyma),

Sequoia

sempervirens^

and Thuja plicada ap-

proximately

600

548 26. SOFTWOOD ANATOMY

Fig.

26-11.

Opposite, paired border pits of

Taxodium distichum with crassulae,

-- 600

In coniferous species, crassulae, thickenings

in the shape of an arc around the pit, as observed

in the radial section, are common (Fig. 22-11).

Spiral thickening oftracheids (Fig. 26-12)

Spiral thickening of tracheids occurs in only

a few species (Douglas—fir, Pacific yew, and the

relatively rare Torreya) so this is an important

characteristic, if present. Douglas—fir may not

have spiral thickening in the latewood tracheids.

Spiral thickening occasionally occurs in the late-

wood tracheids of southern pines (loblolly) and

larix, but these species may also have seasoning

checks. Spiral thickening occurs at a smaller

angle to the longitudinal axis (steeper spirals) in

fibers with thin lumens as in the latewood.

Fig. 26-12. Spiral thickening in Douglas—fir

tracheids, '-'600X.

Compression wood leads to seasoning checks

parallel to the S—2 microfibril angle (Fig. 25-12).

Checks usually form an angle <45° with the

longitudinal axis whereas spiral thickening usually

forms an angle >45°.

Tracheid diameter

Table 26-4 shows the diameters oftracheids.

This can be used to separate some species from

each other. Redwood is very coarse while eastern

redcedar has a very fine texture; compare Figs.

26-52 and 26-44.

Longitudinal parenchyma

Strand (axial or vertical) parenchyma are

never as abundant in the softwoods as in some of

the hardwoods. They are moderately abundant

throughout the growth ring in the families

Taxodiaceae and Cupressaceae and other genera.

These are dijfuse parenchyma when the strands

occur singularly as in redwood (Fig. 26-13) or

baldcypress. When strands are grouped they are

zonate parenchyma which may be banded (the old

term is metatracheal, as in eastern redcedar or

incense cedar) or in clusters as in the hardwoods.

In the coarse—textured species redwood and

baldcypress, they can be barely seen with a hand

lens as streaks on the radial and tangential surfaces

due to their extractives. Strand parenchyma at the

boundaries of the growth rings {marginal or

terminal parenchyma) occur in Abies and Tsuga.

In the heartwood these cells are often filled with

extractives. Longitudinal parenchyma are lacking

in Pinus and Taxus. They occur in the root wood

of Picea, but not in the wood above ground.

The end walls of longitudinal parenchyma of

softwoods are usually nodular, but they are incon-

spicuous in redwood and absent (smooth walls) in

southern pines and Atlantic white—cedar and help

identify these species.

Intercellular spaces

Eastern redcedar has intercellular spaces

between the tracheids where they meet at the

corners. This feature must not be confiised with

compression wood where the same effect is noted.

The pronounced roundness and spiral checks of

compression wood cells help distinguish this from

normal intercellular spaces of eastern redcedar.

Fig. 26-13. Diffuse strand parenchyma of

Sequoia sempervirens show up as dark squares

due to the pitch contents. Resin crystals are

also present at the margin of the growth ring.

26.3 ANATOMY OF SOFTWOOD SPECIES

Table 26-2 helps separate softwoods by

genera. Table 26-3 gives a summary of softwood

features useful in their identification. Table 26-4

gives properties of tracheids.

The uses section includes the properties

MICROSCOPIC ANATOMY OF SOFTWOODS 549

related to the uses of wood. The mechanical

properties are of relevance to wood chipping. The

color section includes the overall appearance.

Many sapwoods are stained with blue stain, a type

of fimgi, that changes the color.

Macroscopic features can be seen with the

unaided eye or with a lOx lens. The terms pores

and vessels are used synonymously. The presence

of tyloses often tends to make the vessels difficult

to see on the cross section with the unaided eye,

so the appearance and the actual sizes of vessels

are not the same. Parenchyma descriptions in this

section refer to longitudinal parenchyma. Most of

the macroscopic cross sections are courtesy of

R.L. Krahmer and A.C. Van Vliet; they are all

the same magnification, about 15~20x. While

the taste of some woods is mentioned, it is not a

good idea to apply this for routine sample identifi-

cation of large numbers of samples.

Softwoods are conveniently classified by their

taxonomy in the order presented in Table 26-3.

Most softwood do not have longitudinal parenchy-

ma observable with the unaided eye or even a

lens.

Softwoods with normal resin canals will

have two ray sizes, the fusiform rays that may be

visible with the unaided eye and the normal rays

that may or may not be visible.

PINACEAE

PINUS

Pines are easily divided into two groups: the

soft pines and the hard, yellow, or pitch pines.

Table 26-2. Separation of softwoods into genera by microscopic features.

Axial resin canals normally present

Axial resin canals absent, unless traumatic

type in tangential

rows

or groups

Epithelial

cells

resin canals are

thin

walled. Ray

tracheids

present

Pinus

Epithelial cells of resin canals are

thick-walled

Tracheids

with

helical thickenings, especial-

ly in early

wood.

Ray tracheids present.

Pseudotsuga

Tracheids rarely with helical thickenings.

Abrupt transition between early wood

and late wood; ray tracheid walls of

late wood rarely with minute

denticulations. . . Larix

Gradual

transition between early wood

and late wood; ray tracheids of late-

wood with minute denticulations

Picea

Axial parenchymapresent

and

conspicuous.

End walls of ray cells not conspicuously

pitted.

Sequoia

Axial parenchyma absent or sparse.

6. End walls of ray parenchyma con-

spicuously pitted, i.e., nodular end

walls.

Abies

6. End walls of ray parenchyma are not

conspicuously pitted.

Thuja

Table 26-3. Anatomical characteristics of coniferous woods useful in their identification.

.tn

'-^ ^ vo r- ^

t^ a r- t^ t^ vo

•a

»n

«r> >n »r>

•^

^ -S

^ ? ^ §

^ b}

O O

5-1

«?

^ vo vo vo vo vo

vo ^ vo vo vo vo

«n

>n m »n «r> »n w^

•Si

•a

Uil i

'^ "^ "^ "^ "^

'^^

S "^

CL,

00 l>

Use this

for

alignment

Resin canals:

Present

Epithelium thin-walled

Latewood transition abrupt

Tracheids

Helical thickening

(s in LW

only)

Bordered pits

2-4

opposite

Bordered pits

2-4

alternate

Rays:

Homocellular

tracheids present

Tracheids present

Tracheids dentate

Indenture

Parenchyma

end

walls nodular

Marginal parenchyma with crystals

Cross—field pitting:

Fenestriform

Pinoid

Piceoid

Cupressoid

Taxodioid

Longitudinal parenchyma:

Present

End walls smooth

End walls nodular

Miscellaneous:

Dimpled tangential surface

Heartwood distinct

Greasy feel

Odor

Use this

for

alignment

1234567890123

XXX

567890123456

X X X X X

VVVXXXX XXXXXXX

XX XX

X X

XXXXXXX

XX XX

XXX

X X X X

XXXXXXX

XXXX

XXX

XXXXXXX

XX XXXXX XXXXXXX

XXXXXXX

X XXXXXXXX

12345678901234567890123456

Key:

indicates characteristic

pronounced;

indicates characteristic

present but

not

pronounced (when used

with

X, it is the

less likely

of the two

choices);

indicates variable according

sample

sources disagree;

indicates sporadic

and may not be of

diagnostic value.

Table 26-3. Anatomical characteristics of coniferous woods useful in their identiHcation, cont'd.

Tf>n-H00ooo\o vo moo <Nmo <srs<NtN

m»noo>n»n«nvo ^n mr-* ^^ovooo oooooooo

a:; a^ a^ a,' a," cx^

Q; a; ft,' c^ a^' o^ E-. tj^ ^ ^ ^

e c ^ . ... . §

s ^ a I s i a I ^ 11 I 8 i

„

s § I 3 I

X X X X X X X

X X

X V X

X X

X V

Use this for alignment 12345678901234567890123456

Resin canals:

Present

Epithelium thin-walled

Latewood transition abrupt

Tracheids

Helical thickening (s in LW only)

Bordered pits 2-4 opposite

Bordered pits 2-4 alternate XXX

Rays:

Homocellular of tracheids present

Tracheids present

Tracheids dentate

Indenture

Parenchyma end walls nodular

Marginal parenchyma with crystals

Cross—field pitting:

Fenestriform X X X X

Pinoid XXX XX

Piceoid X X

Cupressoid X X X X X

Taxodioid X

Longitudinal parenchyma:

Present X

End walls smooth X

End walls nodular X

Miscellaneous:

Dimpled tangential surface x x x

Heartwood distinct XXXXXXX X XX X X

Greasy feel

Identifying odor X

Use this for alignment 12345678901234567890123456

Key: X indicates characteristic is pronounced, x mdicates characteristic is present but not pronounced (when used

with X, it is the less likely of the two choices). V indicates variable according to sample or sources disagree; s

indicates sporadic and may not be of diagnostic value.

552

26.

SOFTWOOD ANATOMY

Table 26-4. Properties of softwood tracheids.

Common name

Baldcypress

Cedar, true: Incense

Cedar, others

Alaska-

Atlantic white-

Port—Orford—

Eastern redcedar

Western redcedar

Northern whitecedar

Douglas—fir, coastal

Fir:

Balsam

California red

Grand

Noble

Pacific silver

Subalpine

White

Hemlock:

Eastern

Western

Larch:

Tamarack

Western

Pine, soft or white:

Jack

Lodgepole

Monterey

Red

Sugar

White, northern

White, western

Pine, hard or yellow:

Ponderosa

Southern U.S.

Loblolly

Redwood

Spruce:

White, etc.

Sitka

Yew, Pacific

Other non U.S.,

Alerce

Almaciga (sakar)

Klinki pine

Parana pine

Scientific name

Taxodium distichum

Libocedrus decurrens

Chamaecyparis nootkatensis

Chamaecyparis thyoides

Chamaecyparis lawsoniana

Juniperus virginiana

Thuja

plicata

Thuja occidentalis

Pseudotsuga menziesii

Abies balsamea

magnifica

grandis

procera

amabilis

lasiocarpa

concolor

Tsuga canadensis

T. heterophylla

Larix

laricina

occidentalis

Pinus banksiana

P. contorta

P. radiata

P. resinosa

P. lambertiana

P. strobus

P, monticola

P. ponderosa

P. taeda

Sequois sempervirens

Picea spp.

P. sitchensis

Taxus brevifolia

Fitzroya cupressoides

Agathis philippinesis

Araucaria klinkii

angustifolia

Diametei

Max.

I^T^^

Ave.

Length^'^

6.0, 6.2

2.0, 3.6

2.1,2.1

2.6

2.8, 2.8

3.8,

3.5

-,2.2

4.5, 3.9

3.5,

3.5

3.3

5.0

4.0

3.6, 3.4

3.2,

3.0

3.5,

3.4

3.5,

3.0

4.0, 4.2

3.5,

3.6

5.0, 5.0

-,3.5

3.5,3.1

3.7, 3.4

4.1,5.9

3.7, 3.0

4.4,

2.9

3.6, 3.6

4.0, 3.6

7.0, 7.0

3.5,

3.3

5.5,5.6

L/Dj,ye

Coarseness^

117

53-95

112

105

100

125

100

120

111

114

101

90-130

100-123

73-110

90-100

121

122

139

mg/100 m

15.4

26-31

24.0

29.0

32.5

18.0

23.0

21.4

19.8

24.0

26.0

23.5

26.8

^Brown and Panshin (1940) p. 112; Panshin and de Zeeuw (1980) p. 133; and Hoadley (1990) p. 17.

^USDA FPL-031 (1923, 1964); ^Isenberg (1981) p. 212.

Fig. 26-14. Southern pine, Pinus spp.

Soft pines have 5 needles per bundle; hard pines

are 2— or 3—needled. Soft pines have a gradual

transition to latewood while hard pines have an

abrupt transition. Slow growth ponderosa pine

ANATOMY OF SOFTWOOD SPECIES 553

may appear like white pine due to its narrow

latewood. The lack of intertracheid pitting on the

radial walls of the latewood of southern pines is

used to distinguish them from the soft

pines.

Hard

and red pines have dentate ray tracheids, whereas

soft pines have nondentate ray tracheids.

The resin canals of P. lambertina and P.

ponderosa are large, while those of P. contorta

and P. resinosa are small for pine resin canals.

Southern

pines (Figs. 26-14 and 26-15)

There are a number of species included in the

group marketed as southern pine lumber. The

most important, and their growth ranges, include:

(1) Longleaf pine

{Pinus

palustris), which grows

from eastern North Carolina southward into

Florida and westward into eastern Texas. (2)

Shortleaf pine (P. echinata), which grows from

southeastern New York and New Jersey southward

to northern Florida and westward into eastern

Texas and Oklahoma. (3) Loblolly pine {P.

taeda),

which grows from Maryland southward

through the Atlantic Coastal Plain and Piedmont

Plateau into Florida and westward into eastern

Texas. (4) Slash pine

{P.

elliotii), which grows in

Florida and the southern parts of South Carolina,

Georgia, Alabama, Mississippi, and Louisiana east

of the Mississippi River.

Grading standards classify lumber from any

one or from any mixture of two or more of these

Fig. 26-15. Loblolly pine

(Pinus taeda)

(50x).