Taxonomy
of Flowering Plants - LECTURE
NOTES - Spring, 1998
Hugh
D. Wilson - rm. 306,
Butler Hall
1 April 1998
The Asteridae
Family Overview - Lamiales
Boraginaceae - the Borage Family
Diversity: Shrubs, trees
and - especially in our flora - herbs in about 100 genera and 2,000 species.
Distribution: Worldwide,
but with greatest diversity in the Mediterranean basin. We have 17 genera
and 82 species in the Texas flora, including 2 endemic
species in the Brazos County flora.
Floral structure:
Significant features: This
family carries the distinctive gynoecium of the Lamiales.
The ovary shows a second septum, producing 4 locules and each of
these has only a single seed. The pericarp is formed around each
seed and, as a result, the gynoecium shows a 4-lobed aspect with a depression
at the center. The syle is therefore not attached to the top
of the ovary, but rather in this central area. This unusual feature,
knows as a gynobasic style, is also
present in the Lamiaceae. However, in contrast to the other
two families of the Lamiales, the Boraginaceae shows three distingishing
features: actinomorphic corolla,
alternate leaves and a terete
stem. Also, as depicted below, many
species of this family produce an inflorescence that uncurls as it develops
- the helicoid or scorpiod
cyme. It is also common for flowers of the Boraginaceae to show
a series of 'bumps' - termed appendages - at the throat of the corolla
and a rough, bristly pubescence.
Local Endemic - Onosmodium
bejariense
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plant
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helicoid cyme
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helicoid cyme - close
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Hackelia
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helicoid cymes uncurled
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flowers with bumpy 'appendages'
at the throat of the corolla
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four parted fruit with each 'nutlet' carrying
a single seed
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More information on the Boraginaceae
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201 homepage, or the Asteridae
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