Plural of exogen; multiple plants that grow by adding layers of wood to their external surface.
Simply the plural form of 'exogen' (Greek 'exo-' outside + 'gen' produce), used when discussing multiple dicotyledonous plants or woody organisms.
Most of Earth's tallest, oldest organisms—like bristlecone pines over 5,000 years old and giant redwoods—are exogens, and we can literally read their entire history in their rings!
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