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Key Features Page

 KEY FEATURES OF FAMILIES AND GENERA

This page summarizes important characteristics for identifying the families and genera of the species that are introduced each week. This material will be presented in Monday lectures. Information for identifying individual species will be presented in Monday and Tuesday laboratories.

GYMNOSPERMAE (class): Gymnosperms

Key features: unprotected seeds, no flowers or fruits, wood composed primarily of tracheids

CONIFERALES (order): Conifers

Key features: cones

CUPRESSACEAE—Cypress family (often called Cedar family)

Family key feature:-- scale-like leaves

Key features of genera:

Genus	Leaves	Branchlets	Cones (scales)
Thuja	scale-like, decussate, lateral leaves curved inward	flattened, planar foliage	oblong, leathery (basal cone scale attachment)
Chamaecyparis	scale-like, decussate, lateral leaves pointed	flattened, planar foliage	globose, leathery (peltate cone-scale attachment
Juniperus	dimorphic- 1) scale-like, decussate 2) awlshaped in 3's	4-angled, bushy foliage	globose, fleshy, berry-like (peltate cone-scale attachment)
Calocedrus	scale-like, whorls of 4	flattened, planar foliage	oblong, leathery, 2 large scales basal cone -scale attachement

 PINACEAE—Pine family

Family key feature: bract and cone-scale distinct, flattened; terminally winged seeds

Key features of Genera:

Genus	Leaves/Twigs	Mature female cone
Pseudostuga	persistent, linear, petiolate leaves, lemon aroma; (very small sterigmata)	pendant, 3-lobe exserted bracts, leathery
Tsuga	persistent, linear, petiolate leaves; small sterigmata	pendant, 1-3 ", leathery
Abies	persistent, linear, sessil leaves with notched apex; smooth, circular leaf scars on twigs	upright, shatter when mature, leathery
Picea	persistent, acicular or linear, sessile, sharp-pointed leaves; twigs with prominent sterigmata	pendent, leathery; entire or wavy cone scales
Larix	deciduous, linear leaves; spirally attached to long shoots AND short shoots	upright to pendent, leathery
Pinus	persistent, acicular, in fascicles	pendent, most woody
Cedrus	persistent, linear leaves; spirally attached to long shoots AND short shoots	upright, shatters when mature, leathery

Pinus

Subgenus	fascicles	fascicle sheath	cone scales	wood
soft pines	usually 5 needles	deciduous	thin, usually unarmed	soft, gradual transition from earlywood to latewood
hard pines	2,3 needles	persistent	thickened at apex, usually armed	hard, abrupt transition from earlywood to latewood

TAXACEAE—Yew family

NOTE: Not a conifer (no cones)

Family key feature: dioecious, female reproductive structure is aril

Taxus key feature—aril

TAXODIACEAE—Redwood family

Family key features: globose to ovoid cone with peltate cone scales, deciduous branchlets (leaves plus small twigs shed as a unit)

Key features of genera:

Genus	leaves	cones
Sequoiadendron	awl-shaped, several ranked	2-3 inches
Sequoia	linear, 2-ranked	1 inch

ANGIOSPERMAE (Class): ANGIOSPERMS

Key features: flowers, seeds protected in fruit, wood composed primarily of vessels, fibers, tracheids

ACERACEAE--Maple family

Family key features: variable

Acer key features: fruit a double winged samara; usually opposite, palmately lobed leaves

BETULACEAE-- Birch family

Family key feature: preformed male aments

Key features of genera:

Genus	female ament
Betula	deciduous bracts (ament shatters when mature)
Alnus	persistent bracts (ament intact when mature)

CORNACEAE-- Dogwood family

Family key feature: none

Cornus key features: most have opposite leaves with arcuate venation, entire margins (all have latex in veins of leaves)

ERICACEAE—Heath family

Family key feature: none

Arbutus key feature: thin red/green exfoliating bark

FABACEAE—Pea family

Family key feature: fruit a legume

Key features of genera:

Genus	Flower/Inflorescence	Leaves	Thorns	Bark
Robinia	bi-laterally symmetrical	1 pinnate	unbranched	ropey
Gleditsia	radially symmetrical,racemes	1 to 2 pinnate	branched	flat ridges

FAGACEAE-- Beech family

Family key feature: involucre (fused bracts) that partially or completely surrounds one or more nuts.

Key features of genera:

Genus	male ament	terminal buds	involucre
Fagus	globose	lanceolate	bracts fused into short spines, surrounds several nuts
Castanea	stiff, upright	small, not distinctive	bracts fused into long, branched spines, surrounds several nuts
Quercus	typical form	clustered	bracts fused into cap; partially surrounding 1 nut

Quercus

subgenus	bark	leaves
white oaks	soft, light colored	rounded lobes
red oaks	hard, dark colored	lobes with bristle tips

white oak key features:

red oak key features:

HAMAMELIDACEAE--Witch Hazel family

Family key features: variable

Liquidambar key features: alternate, stellate (star-shaped ) leaves; fruit a head of beaked capsules

HIPPOCASTANACEAE--Horsechestnut family

Family key features: opposite, palmately compound leaves; showy panicles; fruit a capsule with large brown seed

Aesculus key features: use family features

JUGLANDACEAE--Walnut family

Family key features: pinnately compound, alternate leaves; highly modified female ament (fruit with husk)

Key features of genera:

Genus	male ament	husk	shell	pith
Juglans	single	leather, indehiscent	corrugated	chambered
Carya	groups of 3	woody, dehiscent	smooth	solid

LAURACEAE—Laurel family

Family key features: strong aromatic compounds in leaves, stems, roots; fruit a one-seeded berry or drupe

Key features of genera:

Genus	leaf shape/margin	leaf persistence	tree form
Umbellularia	elliptical, entire	persistent	deliquescent
Sassafras	polymorphic (elliptical, mitten-shaped, 3-lobed), enite	deciduous	excurrent

 

MAGNOLIACEAE—Magnolia family

Family key features: circular stipular scars, large terminal buds (vegetative and reproductive), large terminal flowers and fruits

Key features of genera:

Genus	leaves	fruit
Magnolia	elliptical	aggregate of folicles
Liriodendron	4-lobed truncate	aggregate of samara

 

OLEACEAE- Olive family

Family key feature: variable

Fraxinus key features:opposite pinnately compound leaves, fruit a samara in panicles

PLATANACEAE—Sycamore or Plantetree family

Family key feature: fruit a head of achenes

Platanus key feature (s)—same as family

ROSACEAE-- Rose family

Family key features: variable, flowers generally with 5 unfused petals

Key features of genera:

 

Genus	Leaves	Fruit
Sorbus	variable (simple or pinnately compound)	pome
Prunus	simple, extrafloral nectary	drupe

SALICACEAE--Willow family

Family key features: dioecious; fruit a capsule, abundant, very small seeds with long hairs; abundant vegetative propagation

Key features of genera:

Genus	leaves	buds
Salix	long narrow leaves with short petiole	single budscale
Populus	broad leaves with long petioles	several imbricate budscales

TILIACEAE-- Linden or Basswood family

ULMACEAE—Elm family

Family key feature:variable

Ulmus key features: fruit a samara with wing completely encircling the seed, elliptical, doubly serrate leaf with assymetrical leaf base

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