Taxonomy of Flowering Plants - LECTURE NOTES - Spring, 1998
Hugh D. Wilson - rm. 306, Butler Hall
20 April 1998
The Commelinidae
Family Overview - Commelinales

Commelinaceae  - the Spiderwort Family

Diversity:  Succulent herbs, either annual or (mostly) perennial - ca. 50 genera and 700 species.

Distribution:  Worldwide, but mostly tropical and subtropical with considerable diversity extending into northern temperate regions. We have 6 genera and 24 species in Texas with one endemic genus and five species of Tradescantia known only from Texas (see Texas Endemics and North American taxa).

Floral structure:

Significant features:  Plants of this family show a characteristic vegetative 'fleshy' aspect that often includes a mucilaginous, slimy sap ('snotweed' sometimes applied as a local name) that, on exposure to air, dries to form a weblike mass ('spiderwort').  The alternate, entire, and monocot-like leaves include a sheathing base that is often enclosed around swollen nodes that produce a 'jointed stem'.  While normally actinomorphic, some genera (see below) show reduction of one petal to produce zygomorphy and flowers/inflorescences are often subtended by a spathe.  The sepals, often green, are distinct from the petals which, due to their thin, delicate structure, are often ephemeral (wilting shortly after anthesis - 'day flower').  Many genera have masses of multicellular trichomes attached to the filaments and a subset of the six stamens often show some type of modification (staminodes). 

Commelina erecta - zygomorphic flower (one petal reduced) and spathe
Commelina erecta - sheathing leaf base - swollen node
Commelina erecta - flower close with staminodes (base of photo)

Texas endemic genus - Tinantia anomala (Torr.) C. B. Clarke [Commelinantia anomala (Torr.) Tharp/Tradescantia anomala Torr.]:

Plant with clasping leaves and large spathe
zygomorphic flower with bud,  spathe and strange androecium

flower - front view - all petals equal and all stamens functional
flower - side view - filament hairs
More information on the Commelinaceae

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