Terminology - Leaf, Twig, and Fruit Characteristics
Used in Tree Identification

Familiarization with the following diagrams and terms will make the leaf key and tree descriptions easier to understand and use.  Information provided here is divided into the following topics:

general terms
leaf forms
anatomy of a twig

anatomy of broad leaves
leaf arrangement
leaf margins

leaf tips
leaf bases
types of fruits

 


GENERAL TERMS

leaf — a lateral outgrowth from the stem whose primary function is the manufacturing of food

twig -- a young woody stem to which leaves and buds are attached

branch -- a thicker, older woody stem to which twigs are attached

trunk -- the main vertical stem of a tree

fruit — the seed-bearing portion of a plant

deciduous — trees on which all leaves fall at the end of every season of growth

evergreen — trees on which leaves remain attached for more than one year

 


Black and White drawing illustrating different leaf types of ConifersLEAF FORMS

conifer — a tree with needle or scale-like leaves

fascicle — a dense cluster of leaves or needles (far right)

broadleaf — a tree with wide, flat leaves

 

 

 

 

 

BROADLEAVES

Black and White drawing illustrating leaf shapes of broad leaves


ANATOMY OF A TWIG

Black and White drawing illustrating anatomy of twigterminal bud — a bud that is at the tip of a stem or branch

bud scale — a small modified leaf on the outside of a bud

lateral bud — a bud that is situated along the sides of a branch and not at the tip

lenticel — a corky spot on the bark which originally permitted air to enter the twig

leaf scar — the scar left on a twig when a leaf falls

bud scale scar — the scar left on a twig when a bud scale falls

bundle trace — dot-like scars within a leaf scar, representing the broken ends of ducts which led to the leaf stalk

node — the place on a twig where a leaf is attached

internode — the part of a twig between two nodes

pith — central, usually soft portion of a twig,  chambered piths are divided into empty compartments by cross partitions

thorns and spines (not pictured) — sharp-pointed, rigid structures arising from the twig or leaf


ANATOMY OF BROAD LEAVES

apex — the tip or distal end of a leaf

margin — the outer edge of a leaf blade

leaflet — an individual blade of a compound leaf

midrib — the central or main vein of a leaf

rachis — the midrib of a compound leaf

blade (lamina) — the flat or expanded part of a leaf

petiole — stalk of a leaf

axilary bud — lateral bud located at the base of a leaf petiole

 

compound leaf
— a type of leaf that has three or more leaflets attached to a common stalk

palmately compound — veins or lobes of a leaf radiating from a central point

pinnately compound — arrangement of leaflets attached laterally along the rachis of a compound leaf

  


LEAF ARRANGEMENT

opposite — leaves occurring in pairs at the nodes

alternate — leaves arranged singly at intervals along the stems

whorled — leaves occurring three or more at a single node


LEAF MARGINS

Black and White drawing illustrating leaf margins

entire — a leaf margin that is smooth without teeth or lobes

undulate — a leaf margin that is wavy

serrate — a leaf margin that has pointed teeth that are directed upward

doubly serrate — a serrate leaf margin where the primary teeth support another set of teeth

crenate — a leaf margin that has rounded teeth

lobed — a segmented leaf having pointed or rounded extensions separated by sinuses that do not extend more than halfway to the midrib

sinus — the space or indentation between the lobes of a leaf blade



LEAF TIPS
 

Black and White drawing illustrating leaf tipsacute — slightly pointed

acuminate — sharply pointed

bristle-tipped — sharply pointed tip

truncate — squared or abruptly cut off

obtuse — rounded

 

 

 

 



LEAF BASES

Black and White drawing illustrating leaf basescuneate — wedge-shaped

obtuse — rounded

cordate — heart-shaped

truncate — squared or abruptly cut off

oblique — asymmetrical, unequally sided

 

 

 

 


TYPES OF FRUITS

berry — a simple, fleshy fruit, with seeds embedded in a pulpy mass (persimmon)

drupe — a one-seeded, fleshy fruit with the seed inclosed in a stony wall (cherry, sugarberry, holly)

capsule — a dry fruit which splits open into two or more parts at maturity (sourwood)

legume — a dry fruit with two seams in the outer wall (black locust)

nut — a hard-shelled, dry fruit, sometimes with a outer covering or husk (hickory, oak acorn, black walnut)

dehiscent — the opening by slits or valves of an outer fruit covering

indehiscent — an outer fruit covering that does not open by slits or valves

pome — a fleshy fruit, with seeds incased by a papery wall (apple)

nutlet — a small nut

samara — a winged, one-cell, one-seeded, dry fruit (elm; double samara — maple)

multiple — a fruit formed from several flowers into a single structure having a common axis

multiple of capsules -- sweetgum
multiple of follicles — magnolia
multiple of samaras — yellow-poplar, ash
multiple of nutlets — sycamore, birch

Black and White drawing illustrating four different fruit multiples from trees

follicle — a dry fruit with one seam in the outer wall

pendant — hanging or drooping

globular — spherical

bracts -- small leaf or leaf-like structures beneath a flower or flower cluster that sometimes become protectors of the fruit

 


 

INTRODUCTION TERMINOLOGY LEAF KEY TREE LIST EXERCISES