An Illustrated Guide to Arizona Weeds

The University of Arizona Press


Achene - A small dry one-seeded fruit in which the ovary wall is free from the seed

Anther - Enlarged part at the top of the stamen; bears the pollen

Awn - A bristle or spine, as at the tip of some bracts of grasses

Axil - The upper angle between the stem and the leaf

Bract - A modified leaf underneath a flower or inflorescence

Bur - A rough or prickly envelope around a seed or fruit

Calyx - The outer set of floral leaves, usually green, composed of all the sepals

Corolla - The set of floral leaves, usually showy, composed of all the petals

Deciduous - Dropping off; shedding of leaves at the end of the growing season

Dehiscent - Splitting open at maturity

Disk flowers - The tubular flowers in the center of the flower heads in the sunflower family

Embryo - A young plant enclosed in a seed

Floret - A small flower in the spikelet of the grasses, or the flower head of the sunflower family

Flower head - A dense inflorescence of stalkless flowers

Frond - The leaf of a fern

Fruit - The seed case or seed pod (the ripened ovary); containing anywhere from one to many seeds

Glands - Secreting tissue

Glumes - A pair of bracts at the base of the grass spikelet

Grain - The seedlike dispersal unit of the grass family

Inferior ovary - Where the sepals, petals, and stamens appear to rise from the very top of the ovary

Inflorescence - The arrangement of flowers on a stalk where several are present, as a spike, raceme, head, panicle

Involucre - A cluster of bracts

Keel - A central dorsal ridge; the two united petals in some legume flowers

Leaflet - A division of a compound leaf

Mycorrhiza - Formed by a combination of underground threads and rootless

Node - That position on the stem where a leaf, leaves, or branch arises

Nutlet - A small nut; the one-seeded portion of a larger fruit that separates at maturity

Ovary - Base of the female part of the flower (pistil); ripens into the fruit

Panicle - A loose, irregularly branched inflorescence with stalked individual flowers

Pappus - The modified calyx of a disk or rayflower in the sunflower family

Petaloid - Petallike

Ray flower-Marginal petallike flowers in the inflorescence of the sunflower family

Rhizome - A horizontal underground stem

Rosette - A cluster of spreading or radiating basal leaves

Runner - A horizontal aboveground stem; a stolon

Sepal - One of the outer set of floral leaves or calyx, usually green

Sheath - The basal portion of the leaf which clasps the stem

Spike - An unbranched inflorescence in which the flowers are not stalked

Spikelet - The unit of the inflorescence in grasses

Stamen - The male portion of the flower

Stipule - One of a pair of appendages at the base of the leaf

Stolon - A horizontal, underground stem

Succulent - Soft and fleshy in texture

Tuber - A swollen underground stem

Volva - The membraneous envelope enclosing an immature mushroom

Whorl - Three or more leaves or flowers arising from the same node

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