Taxonomy of Flowering Plants - LECTURE NOTES - Spring, 1998
Hugh D. Wilson - rm. 306, Butler Hall
13 April 1998
The Arecidae
Family Overview - Arales

Lemnaceae  - the Duckweed Family

Diversity:  Floating or submerged aquatics found in or on freshwater habitats throughout the world.  The family includes about 6 genera and about 29 species.

Distribution:  Worldwide with extensive species level distributions mediated by migratory birds. We have 4 genera and 15 species in Texas.

Floral structure - imperfect, reduced to the max: 

 
Significant features:  The smallest flowering plants adapted, via extreme reduction (no stem, leaves, root), for occupation of surface water (maximum light, minimum competition).  This adaptive syndrome includes algal-like vegetative reproduction via clonal 'budding' of the plant body or thalus with sexual reproduction very rare.  Linkage between this family and the Araceae is similar to other family pairs we have examined - Monotropaceae and Ericaceae (Ericales) and Convolvulaceae and Cuscutaceae (Solanales) - in that the affinity between the two families is clear and the smaller element represents an extreme of trends that are evident among taxa of the larger.


Fruit and Floral Structure:
 
Wolffia globosa plant (center) with fruit (top) and eye of a needle (bottom) from the World's Smallest Fruit page
Lateral view of flowering Wolffia borealis  - monoecious with a single staminate flower (an) and pistillate flower (pi) - from Wayne P. Armstrong's Key to the Lemnaceae of western North America

Plants and populations:
 
Lemna gibba population along the shoreline of Lake Hodges in San Diego County, California (from the Lemnaceae homepage)
Interspecific variation (6 species) in Wolffia - from Lemnaceae Homepage
 
Lemna gibba - plants in flower (from Plant Systematic Collection - University of Wisconsin)
Mixed population - Lemna and Wolffia - from Wisconsin Botany (from Plant Systematic Collection - University of Wisconsin)

More information on the Lemnaceae 


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