Section A. Structure and Specialized Characters:
III. Stems

A. Stem Parts (Figure 6-1-2)

1. Twig Surface Parts

Bud. An immature shoot.

Internode. A section or region of stem between nodes.

Leaf Scar. A mark indicating former place of attachment of petiole or leaf base.

Lenticel. A pore in the bark.

Node. Region of stem from which a leaf, leaves, or branches arise.

Prickle. A sharp pointed outgrowth from the epidermis or cortex of any organ.

Stipular Scar. A mark indicating former place of attachment of stipule.

Terminal Bud Scale Scar Rings. Several marks in a ring indicating former places of attachment of bud scales.

Vascular Bundle or Trace Scar. A mark indicating former place of attachment within the leaf scar of the vascular bundle or trace.

2. Major Stem Parts

Bark. Tissues of plant outside wood or xylem.

• Exfoliating Bark. Bark cracking and splitting off in large sheets.
• Fissured Bark. Split or cracked bark.
• Plated Bark. Split or cracked bark with flat plates between fissures.
• Ringed Bark. Split or cracked bark with circular fissures.
• Shreddy Bark. Soft but coarse fibrous bark, usually shallowly fissured.
• Smooth Bark. Bark without fissures.
• Winged Bark. Bark with one or more thin, flat longitudinal expansions or elongate plates.

Pith. Centermost tissue of stem, usually soft.

• Chambered Pith. Solid core of pith cells absent, only distinct partitions present.
• Continuous Pith. With solid core of parenchyma or pith cells.
• Diaphragmed Pith. With solid core of pith cells and distinct partitions.
• Hollow Pith. Disintegrated pith with a large central cavity.
• Spongy Pith. Porous, easily compressible pith.

Wood. Xylem consisting of vessels and/or tracheids, fibers, and parenchyma cells.

• Annual Ring. Usually one year's growth of wood; spring and summer wood.
• Diffuse Porous Wood. Annual rings with vessels or pores more or less evenly distributed.
• Non-porous Wood. Annual rings with tracheids only, no vessels produced in spring or summer wood.
• Ring Porous Wood. Annual rings with vessels or pores usually in the spring wood, in a well defined circular band.

B. Stem Types (Figure 6-2-1)
(Classification based on habit, direction of growth, or position)

Arborescent. Tree-like in appearance and size.

Ascending. Inclined upward.

Cespitose. Short, much-branched, plant forming a cushion.

Clambering. Sprawling across objects, without climbing structures.

Climbing. Growing upward by means of tendrils, petioles, or adventitious roots.

Columnar. Erect with a stout main stem or trunk.

Decumbent. Reclining or lying on the ground with the tips ascending

Dichotomous. With equally forked branches or stems.

Eramous. With unbranched stems.

Erect. Upright.

Fastigiate. Strictly erect and parallel.

Fruticose. Shrubby.

Geniculate. Abruptly bent at a node, zigzag.

Procumbent, Prostrate, or Reclining. Trailing or lying flat, not rooting at the nodes; humistrate.

Ramose. Branched.

Repent. Creeping or lying flat and rooting at the nodes.

Soboliferous. With loosely clumped shoots arising some distance apart from rhizomes or under ground suckers.

Stoloniferous. With runners or propagative shoots rooting at the tip producing new plants; bearing stolons; sarmentose.

Strict. Stiff and rigid.

Supine. Prostrate, with parts oriented upward.

Trailing. Sprawling on ground, usually with adventitious roots.

Twining. Coiling around an object.

Virgate. Wand-like; long, slender, and straight.

C. Stem Structural TypesFigure 6-2-2)

Bulb. A short, erect, underground stem surrounded by fleshy leaves.

Bulbel. A small bulb produced from the base of a larger bulb.

Bulbil. A small bulb or bulb-like body produced on above ground parts.

Bulblet. A small bulb, irrespective of origin.

Caudex. A short, thick, vertical or branched perennial stem usually subterranean, or at ground level.

Cladode (phylloclad). A flattened main stem resembling a leaf.

Corm. The enlarged, solid, fleshy base of a stem with scales; an upright underground storage stem.

Cormel. Small corm produced at base of parent corm.

Culm. Flowering and fruiting stems of grasses and sedges.

Pachycauly. Short, thick, frequently succulent stems, as in

Primocane. The first year non-flowering stem, as in most blackberries; a turion.

Pterocauly. Winged stems.

Rhizome. A horizontal underground stem.

Rootstock. A term applied to miscellaneous types of underground stems or parts.

Runner or Stolon. An indeterminate, elongate, above ground propagative stem, with long internodes, rooting at the tip forming new plants.

Sarcocauly. Fleshy stems.

Scape. A naked flowering stem with or without a few scale leaves, arising from an underground stem.

Sclerocauly. Hard, dryish stems.

Spur. A short shoot on which flowers and fruits or leaves are borne.

Sucker. A shoot arising below ground or from an old stem, usually fast-growing and adventitious; surculose.

Tendril. Long, slender, coiling branch, adapted for climbing (most tendrils are leaf structures).

Thorn. A sharp-pointed branch.

Tiller. A grass shoot produced from the base of the stem.

Tuber. A thick storage stem, usually not upright.

Turion. An over-wintering bud, as in Lemna.

Underground Stolon. A determinate, elongate, underground propagative stem with long internodes forming a bulb or tuber at the tip.