WOOD & HERBACEOUS STEM ANATOMY

Bark
cork
cortex
endodermis
Phloem
2^o Cambium
phloem
xylem
(1^o elongation: shoots, twig tips)
Pith
Rays

2^o Xylem (wood)
Sections:
Radial
Tangential
Cross-section
Rings
Early Wood
less dense, lumina wider, walls thinner
Late Wood
dense, relatively thick walls
Transition: abrupt, gradual

CONIFER WOOD "softwoods"

Non-Porous: without vessels
Water Transport by Tracheids

resin canals (i.e. radial canals [also: axial, traumatic])
e.g., Larix, Pinus, Picea, Pseudotsuga
without resin canals
e.g., Abies, Calocedrus, Sequoia
Tracheids:

Border Pits


Spiral Thickenings
Cracks

Rays
Fusiform (with resin canal)
Uniseriate
Parenchyma (heterogenous)

upright, procumbent
Ray Tracheids

thickened walls, slanting ends, ± teeth
± Nodular Endwalls ( & parenchyma)
Cross-Field Pitting: rays X parenchyma

Cell Wall

ANGIOSPERM WOOD "Hardwoods"

Porous: with vessels (trachea)
Diffuse Porous
vessels scattered throughout annual rings
and/or uniform in size
e.g., Tilia, Juglans, Betula
Ring Porous
vessels collected in one part of ring
and/or larger in early wood
e.g., Fraxinus, Quercus, Ulmus
Vessel ends
Open Fagus

Sieve Plates Liriodendron scalariform
Pits (between vessels)
Scalariform Magnolia elongate, spiral
Opposite Liriodendron round, rows
Alternate Acer, Populus
Rays (parenchyma)
Uniseriate, multiseriate
homogeneous
heterogenous (upright, procumbent)
Parenchyma
Paratrachial (associated with vessels)
Scanty Acer
Vasicentric Morus
Aliform Fraxinus
Banded Confluent
Boundary
Terminal Populus
Apotrachial (not surrounding vessels)
diffuse e.g., Quercus
banded e.g., Tilia
Tyloses: outgrowth of parenchyma cell into vessel, forming partial or complete blockage of lumen

HERBACEOUS STEM

Wood absent: Vascular bundles scattered in cortex of stem.

Dermal
Epidermis, Stomata, Cuticle, Collenchyma
Fascicular, Vascular
Vascular Bundles (see types below)
Phloem, Cambium, Xylem
Interfascicular Region
Fundamental
Cortex
Pith: Starch, Sheath, Endodermis, Casparian Strips (occasional)

Conifers and Angiosperms
Vascular Ring between Cortex and Pith
Monocotyledons
• Two Vascular Rings: Avena, Hordeum, Secale, Triticum, Oryza
  
• Scattered Vasc. Bundles: Bambusa, Saccharum, Sorgum, Zea
  
• Also: outer ring embedded in sclerenchyma Layer
Vines: wide rays (=interfascicular) with bands of perivascular fibers

• Collateral Phloem (Phloem outside xylem): most common
• Bicollateral Phloem (Phloem both sides): Apocynaceae, Asclepiadaceae, Convovulaceae, Cucurbitaceae, Solanaceae, some Compositae
  
• Amphicribal Bundles (Phloem around Xylem): Ferns, some Angiosperms
  
• Amphivasal Bundles (Xylem around Phloem): Rheum, Rumex, Mesembryanthemum, Begonia, Araceae, Liliaceae, Juncaceae, Cyperaceae
  
• Alternating layers of Xylem and Phloem: Amaranthaceae, Chenopodiaceae, Menispermaceae, Nyctaginaceae

Conifer Wood

Cross Section

Radial Section

Tanjential Section

Angiosperm Wood

Herbaceous Stem

Cucurbita
Zea