caudex

{{Short description|Biological structure in a plant stem}}

Image:Dicksonia_antarctica_(Tasmanian_Fern_Tree).jpg, but has a different structure.]]

Image:Jatropha cathartica2 ies.jpg is pachycaul, with thickening that provides water storage.]]

A caudex ({{plural form}}: caudices) of a plant is a stem,{{cite book|author1=Hickey, M. |author2=King, C. |year=2001|title=The Cambridge Illustrated Glossary of Botanical Terms|publisher=Cambridge University Press}} but the term is also used to mean a rootstock{{cite book|author=Stearn, W.T.|year=1992|title=Botanical Latin: History, grammar, syntax, terminology and vocabulary, Fourth edition|publisher=David and Charles}} and particularly a basal stem structure from which new growth arises.{{cite book|author=Simpson, M.G.|year=2010|title=Plant Systematics: Second Edition|publisher=Elsevier Science|isbn=9780080922089|url=https://books.google.com/books?id=dj8KRImgyf4C&q=caudex}}pages 456 and 695

In the strict sense of the term, meaning a stem, "caudex" is most often used with plants that have a different stem morphology from the typical angiosperm dicotyledon stem: examples of this include palms, ferns, and cycads. The largest of all caudices is that of the ombu (Phytolacca dioecea) of the Pampas of South America which can be fifty feet (fifteen meters) thick.William Henry Hudson, "Far Away and Long Ago" (1918) New York: E.P. Dutton page 5

The related term caudiciform, literally meaning stem-like, is sometimes used to mean pachycaul, thick-stemmed. Caudices should not be confused with lignotubers which can also be very large.