Ambrosia L.

First published in Sp. Pl.: 987 (1753)
This genus is accepted
The native range of this genus is New World, Macaronesia, Africa, Madagascar, Medit to Arabian Peninsula.

Descriptions

Compositae, H. Beentje, C. Jeffrey & D.J.N. Hind. Flora of Tropical East Africa. 2005

Morphology General Habit
Annual or perennial herbs, less often shrubs, aromatic
Morphology Leaves
Leaves alternate or sometimes opposite
Morphology Reproductive morphology Inflorescences Capitulum
Capitula unisexual, monoecious Female capitula solitary, axillary to upper leaves but below male heads, sessile, 1-flowered; involucre enveloping the achene, becoming hardened, with 4–6 small spines; corolla absent; style branches long and linear, exserted from involucre Male capitula small, in racemes or spikes; involucre cupuliform, of connate phyllaries; corolla tubular; anthers ± free, with linear apical appendage; ovary abortive
sex Male
Male capitula small, in racemes or spikes; involucre cupuliform, of connate phyllaries; corolla tubular; anthers ± free, with linear apical appendage; ovary abortive
sex Female
Female capitula solitary, axillary to upper leaves but below male heads, sessile, 1-flowered; involucre enveloping the achene, becoming hardened, with 4–6 small spines; corolla absent; style branches long and linear, exserted from involucre
Morphology Reproductive morphology Fruits
Achenes ovoid, smooth, enveloped in hardened involucre; pappus absent.
[FTEA]

George R. Proctor (2012). Flora of the Cayman Isands (Second Edition). Royal Botanic Gardens, Kew

Morphology General Habit
Monoecious (rarely dioecious) annual or perennial herbs, sometimes woody at the base; leaves opposite or alternate (rarely in whorls of 3), entire to pinnately cut or dissected
Morphology Reproductive morphology Flowers
Staminate heads in spikes or racemes, the pistillate solitary or in glomerules at the base of the staminate raceme
Morphology Reproductive morphology Inflorescences Bracts Involucre
Staminate involucre hemispheric or saucer-shaped, 5–12-lobed; receptacle flat, naked or scaly; florets funnel-shaped, 5-toothed; anthers scarcely coherent, mucronate- tipped; style undivided, capitate-penicillate
Morphology Reproductive morphology Flowers Gynoecium Pistil
Pistillate involucre closed, usually with small tubercles or prickles near the top and contracted above into a short beak surrounding the style; corolla absent; style deeply divided into 2 long, narrow arms
Morphology Reproductive morphology Fruits
Achenes broad and thick, without a pappus, closely surrounded by the persistent, hardened involucre.
Distribution
A mostly American genus of between 35 and 40 species.
Note
The wind-borne pollen of some species is a principal cause of hay-fever.
[Cayman]

Sources

  • Flora of Tropical East Africa

    • Flora of Tropical East Africa
    • http://creativecommons.org/licenses/by-nc-sa/3.0

  • Flora of the Cayman Islands

    • Flora of the Cayman Islands
    • http://creativecommons.org/licenses/by-nc-sa/3.0

  • Herbarium Catalogue Specimens

  • Kew Names and Taxonomic Backbone

    • The International Plant Names Index and World Checklist of Vascular Plants 2024. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 International Plant Names Index and World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0

  • World Checklist of Vascular plants (WCVP)

    • The International Plant Names Index and World Checklist of Vascular Plants 2024. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0