The Taxaceae

"The Yew Family"

Taxus baccata with fleshy aril	Taxus baccata tree
The English Yew	The English Yew

The Taxaceae family is comprised of 5 genera made up of 20 different species. Taxus, the major genus of the family is made up of 10 species and the Torreya genus has 4 species. These plants are found mostly in the Northern Hemisphere, extending south to Guatamala and Java, with one monotypic genus endemic to New Caledonia. Taxaceae tend to grow in damp valley bottoms where leaf littler accumulates.

Click here for a distribution map of the Taxaceae in the U.S.A.

Vegetative Characters | Reproductive Characters | Diagnostic Characters | Economic Importance/Fun Facts | Evolutionary Adaptations and Relationships | Glossary of Terms | References and Links | Pictures

Vegetative Characters

• small to moderately sized trees or shrubs
• leaves simple, persistant for several years
• leaves alternate (opposite in one species)
• leaves linear or linear-lanceolate, flattened, entire, acute at apex
• leaves sometimes twisted so as to appear 2-ranked
• leaves with a single vein and with or without a resin canal
• trunks are simple, erect, and slightly buttressed
• bark is thin, fibrous, and weakly scaling
• wood is hard, heavy, dense, and extremely resilient

Reproductive Characters

• dioecious (rarely monoecious)
• microsporangiate strobili with 6-14 microsporophylls
• ovules solitary and cones lacking
• ovules are borne terminally on an ovuliferous branch
• seeds with a hard outer layer, associated with a fleshy, usually brightly colored aril (see picture below)
• wingless pollen grains (little is known or reported about the characteristics of the pollen grains)

Diagnostic Characters

• unique among conifers because their solitary seed is not associated with cone scales or structures resembling them
• usually aromatic
• slow growing
• woody shrubs or trees
• bright colored (usually red) fleshy arils

Economic Importance/Fun Facts

• All parts of the plant are poisonous with the excpetion of the fleshy aril.
• Taxus contains taxol, one of the highly poisonous alkaloids in the leaves, stems, and seeds.
• Taxol's very potent antimitotic activity makes it a potential use as an anticancer chemotherapeutic compound..
• Taxus is widely grown as an ornamental in North America and Europe.
• The wood of Torreya, its edible seed, and seed oil are valued in Asia.
• The wood of most species was widely used for making archer's bows.

Evolutionary Adaptations and Relationships

• The Taxaceae have recently been removed from the order coniferales (because their seeds are not borne in cones) and placed (the only family) in the order Taxales.
• They have also been placed in a distinct Suborder, Taxineae Luerss (1879.
• They have even been segregated at the Subclass rank as Taxidae (Ehrend. ex Reveal 1996).
• Some authors have assigned amentotaxus to a separate family (Amentotaxaceae Kud & Yamam. 1931), likewise austrotaxus (Austrotaxaceae Nakai 1938) and torreya (Torreyaceae Nakai 1938).

Glossary of Terms

• Endemic - of or found only in one area.
• Aril - an additional integument that is formed on some seeds after fertilization; an outgrowth that forms a fleshy bag which may completely or partially surround the seed; may be spongy, fleshy, or hairy and is often brightly colored
• Buttress - on certain trees, the branch roots or other aboveground portions of the trunk or root that arch away from the trunk before they reach the soil, forming additional props; prop roots

References and Links

• http://www.csdl.tamu.edu/FLORA/mi10/mi10015.jpg
• http://web1.manhattan.edu/fcardill/plants/gymno/taxus1.jpg
• http://www.csdl.tamu.edu/FLORA/cgi/b98_map?family=TAXACEAE
• http://pharm1.pharmazie.uni-greifswald.de/systematik/thumbnails/taxale3.jpg
• http://www.hort.uconn.edu/plants/campus/vermont/11/3/3.jpg
• http://www.dem.de/entertainment/cybergarten/gartenblumen/t/taxus_cuspidata.jpg
• http://snr.uvm.edu/www/mac/plant-id/gymnosperms/taxaceae/canadayewhabit.gif
• http://www.harcourt.com/dictionary.html
• Kramer and Green, 1990. The Families and Genera of Vascular Plants. Springer-Verlag. New York, NY U.S.A.
• Judd et al., 1999. Plant Systematics: a phylogenetic approach. Sinauer Associates, Inc. Sunderland, MA U.S.A.
• http://www.biologie.uni-hamburg.de/b-online/earle/ta/

Pictures

Taxus cuspidata aril	Taxus media on the campus of the University of Connecticuit

Taxus cuspidata	Taxus canadensus a low, sprawling shrub in its natural habitat

For questions or feedback, contact: Kelly McKay