Dioon edule

Lateral budding is present and mucilage, or sap, is excreted from any cut surfaces on the plant body.

The plant has a large central medulla and a single vascular bundle containing the xylem, phloem and cambium.

Since the organism is slow-growing and xerophilous (i.e. drought-tolerant), only a small conduction channel is needed, unlike other plants.

D. edule has three or four large adventitious (i.e. abnormally positioned) roots surrounded by many smaller ones which harbor small nodules containing tannins.

Most of the areas in which D. edule resides are subjected to very dry climates and frequent brush fires which impact their survival and distribution.

It is found mostly on shallow, rocky soils due to competition with other, faster growing species for water, nutrients and seed dispersal.

In response, they have developed a selective advantage for growing in these harsh climates including vigorous tap roots for anchorage and water conduction.

In addition to competition, causal agents of D. edule's random, clumped distribution include predation, variations in temperature and precipitation, and measures of seed dispersal.

This is reasonably unusual because cycad seeds and foliage are poisonous to most mammals, excluding these varied species of rodents.

It is also speculated that the narrower leaves are endemic in the northern subspecies due to less temperate and humid environmental conditions in these areas.

The United States Botanical Garden suggests that plant material should be conserved, seed banks should be established and legislation regarding trading cycads and protection of their habitats should be implemented and enforced.

edule is commonly called the chestnut dioon and is endemic to the eastern coast of Mexico.