Alternate

Leaves are attached to the stem singly, not in opposite pairs.

Basal

Leaves attached at the base of a stem in a tight cluster.

Opposite

Leaves attached in pairs to each side of a twig or a shoot.

Whorled

Arranged along a twig or shoot in groups of three or more at each node.

Apex

The tip of the leaf, the point farthest from attachment.

Base

The end of the leaf blade nearest to the point of attachment.

Blade

The broad part of the leaf.

Leaflet

One of the leaflike parts of a compound leaf.

Midvein

The central vein of a leaf.

Petiole

The leaf stalk

Petiolule

The stalk of a leaflet of a compound leaf.

Stipule

A small leaflike appendage to a leaf, usually borne in pairs at the base of the leaf stalk.

Tendril

A slender, twining organ used to grasp support for climbing.

Crenate

Margins with continuous, rounded, and generally outward-pointing teeth; dentate with conspicuously rounded teeth.

Crenulate

Very small rounded teeth along the margins.

Dentate

Margins with continuous, generally outward-pointing teeth.

Denticulate

Dentate with very small teeth.

Entire

Margins without teeth or serrations. 

Serrate

Margins with continuous, sharp, forward-pointing teeth, like the blade of a ripsaw.

Serrulate

Toothed along the margin with minute,sharp, forward-pointing teeth.

Sinuous or sinuate

Margins with more or less wavy or sinuous structure in the plane of the leaf.

Toothed

Margins more or less toothed. The term is generic and encompasses the terms serrate, dentate, and crenate, which describe different types of relatively fine, continuous toothing, as well as situations where the teeth are widely spaced, large and lobe-like, or occur at different scales (doubly toothed).

Undulate

Margins wavy or undulating out of the plane of the leaf.

Auriculate

When a simple leaf divided at the base into two leaf-like appendages

Cordate

Heart-shaped, with the notch at the base.

Elliptical

Leaves shaped like an ellipse; that is, generally symmetrical, elongated, and more or less evenly rounded at both ends.

Hastate

Arrowhead-shaped, but with the basal lobes turned outward rather than downward; halberd-shaped.

Lanceolate

Shaped like a lance head; tapering to a point on each side, long.

Synonyms

lance-shaped

Linear

Resembling a line; long and narrow with more or less parallel sides.

Oblong

Two to four times longer than broad with nearly parallel sides.

Obovate

Inversely ovate, with the attachment at the narrow end.

Orbicular

Circular or rounded. The overall shape of the leaf is rounded or orb-like.

Ovate

Egg-shaped in outline and attached at the broad end.

Peltate

Shield-shaped; borne on a stalk attached to the lower surface rather than to the bae or margin.

Pinnatifid

Pinnately divided, but not all the way down to the central axis

Sagittate

Arrowhead-shaped, with the basal lobes directed downward.

Cauline

Positioned along the stem, as opposed to basal leaves.

Compound

A leaf separated into two or more leaflets.

Dissected

Deeply divided into many narrow segments.

Lobed

Leaves with distinct protrusions (lobes), either rounded or pointed and cut less than half-way to the base or midvein.

Palmate

Lobed, veined, or divided from a common point like the fingers of a hand.

Perfoliate

A leaf with the margins entirely surrounding the stem so that the stem appears to pass through the leaf.

Pinnate

A compound leaf with leaflets arranged on opposite sides of an elongated axis.

Simple

Leaf-blade is not separated into leaflets, though the blade may be deeply lobed or toothed.

Palmate veins

Venation pattern where several main veins radiate from one point where the petiole and leaf blade unite

Parallel veins

Venation pattern where the veins run parallel except where they meet at the tip and the base.

Pinnate Veins

Venation pattern where the main vein extends from the base to the top of the leaf. Smaller veins are produced from the main vein.

Anther

Part of a stamen that produces and contains pollen.

Calyx

The outer perianth whorl; a collective term for all of the sepals of a flower.

Carpel

Female reproductive organ of a flower consisting of stigma, style, and ovary.

Corolla

The collective name for all of the petals of a flower; the inner perianth whorl.

Filament

The stalk of a stamen bearing the anther at its apex.

Labellum

Central petal at the base of an orchid flower

Perianth

The calyx and corolla of a flower, collectively, especially when they are similar in appearance.

Pistil

The female reproductive organ of a flower, typically consisting of a stigma, style, and ovary (called a carpel) or several carpels fused together.

Pistillate

The female flower(s)

Sepal

A segment of the calyx.

Stamen

The male reproductive organ of a flower, consisting of an anther and filament; the angiosperm microsporophyll.

Staminate

The male flowers

Stigma

Part of the pistil, forms the distal portion of the style.

Style

The part of a pistil of a flowering plant that encloses an ovary. A pistil may consist of a single carpel or of several carpels joined together.

Tepal

A segment of a perianth which is not differentiated into calyx and corolla; a sepal or petal

Actinomorphic

Radially symmetrical, so that a line drawn through the middle of the structure along any plane will produce a mirror image on either side.

Zygomorphic

Bilaterally symmetrical, so that a line drawn through the middle of the structure along only one plane will produce a mirror image on either side.

Axillary

Arises from a leaf axil

Synonyms

axillary inflorescence

Terminal

Terminates the growth of the branch

Synonyms

terminal inflorescence

Bract

Modified/specialized, usually small, leaflike structure often positioned beneath a flower or inflorescence.  Often confused with flower petals.

Disk

The central portion of the involucrate head bearing tubular or disk flowers in the Asteraceae.

Floret

A small flower; an individual flower within a dense cluster, as a grass flower in a spikelet, or a flower of the Asteraceae in an involucrate head.

Flower

The reproductive portion of the plant consisting of stamens, pistils, or both, and usually including the perianth of sepals or both sepals and petals.

Involucre

A whorl of bracts subtending a flower or flower cluster.

Pedicel

The stalk of a single flower in an inflorescence, or of a grass spikelet.

Peduncle

The stalk of a solitary flower or of an inflorescence.

Ray

1. An inflorescence branch in an umbel.

2. Petal-like parts in the ray flowers of Asteraceae.

Spathe

A large bract or pair of bracts forming a sheath to enclose the flower cluster of certain plants such as Jack-in-the-Pulpit.

Catkin

An inflorescence consisting of a dense spike or raceme of apetalous, unisexual flowers.

Corymb

A flat-topped or round-topped inflorescence, racemose, but with the lower pedicels longer than the upper.

Cyme

A flat-topped or round-topped determinate inflorescence, paniculate, in which the terminal flowers bloom first.

Head

A dense cluster of sessile or subsessile flowers; the involucrate inflorescence of the Asteraceae.

Panicle

A branched, racemose inflorescence with flowers maturing from the bottom upwards.

Synonyms

paniculate

Raceme

An unbranched, elongated inflorescence with pedicellate flowers maturing from the bottom upwards

Spadix

A spike with small flowers crowded on a thickened axis.

Spike

An unbranched, elongated inflorescence with sessile or subsessile flowers or spikelets maturing from the bottom upwards.

Umbel

A flat-topped or convex inflorescence with the pedicels arising more or less from a common point, like the struts of an umbrella; a highly condensed raceme.

Annual constriction

The term describes a section of stem that looks narrower than the rest of the stem due to presence of smaller and occasionally also more congested leaves.  These indentations mark the start of each seasonal growth.

Appressed

Leaf is lying close to or pressed against the stem or stipe.

Ascending

Leaf is growing at an upward angle relative to the stem.

Rank

When looking down along the stem, you notice that the leaves line up in rows or ranks.  If a pair of leaves is positioned at the 90-degree angle with respect to the pair above or below, then the leaves are 4-ranked.  In case every three pairs of leaves are offset from each other, the leaves are 6-ranked.

Reflexed

Leaf bent backward relative to the stem

Sporophyll

Specialized leaf bearing a sporangium.

Spreading

Leaf is at an angle from ascending to perpendicular to the stem.

Strobilus

A cone, that is, a region of the stem that bears only specialized leaves - sporophylls.

Gemmae

Produced in the upper portion of mature stems.

Stomates

Air pores on the surface of leaves.

Cavity

Large, hollow center in the stem or branches.

Cone

Each fertile stem forms a spore-bearing cone at the top, which consists of an axis and specialized leaves (also called scaled) bearing sporangia (spore cases). 

Internode

Stem or branch section between the nodes.

Node

A swollen, solid(not hollow) area of the stem; also, point where branches attach to the stem.

syn: joint

Rhizome

Underground organs structurally similar to stems and branches, ranging in length from a few inches to many feet, spreading extensively, with new stems or rootles sprouting from their nodes.

Ridge

Elevated lines on the surface of stems/branches and separated by grooves.

Sheath

Generally, a tubular part of a leaf enclosing the stem.  In a horsetail, tiny modified leaves are whorled at each node and fused at edges, collectively forming a cylindrical toothed sheath.

Achene

A dry fruit that does not separate or split open when mature, formed from one carpel and containing a single seed.

Acorn

The hard, dry fruit of oaks with a single large seed and a cuplike base.

Berry

A fleshy fruit developing from a single pistil, with several or many seeds, such as tomato. Sometimes applied to any fruit which is fleshy or pulpy throughout, i.e. lacking a pit or core.

Bur

A fruit armed with barbed or hooked spines or appendages.

Capsule

A dry, dehiscent fruit composed of more than one carpel.

Drupe

An indehiscent fruit in which an outer fleshy part surrounds a single shell (for example the bit) of hardened endocarp with a seed (kernel) inside.

Follicle

Dry unilocular fruit formed from one carpel

Legume

A dry, dehiscent fruit derived from a single carpel and usually opening along two lines of dehiscence as in a pea pod.

Samara

A dry, indehiscent, winged fruit, such as in maples